1 00:00:00,000 --> 00:00:14,893 [SQUEAKING] [RUSTLING] [CLICKING] 2 00:00:14,893 --> 00:00:16,560 SARAH HEWETT: All right, good afternoon. 3 00:00:16,560 --> 00:00:18,630 We're going to get started because we have a lot 4 00:00:18,630 --> 00:00:22,140 to talk about for this one lab before a lot of you guys 5 00:00:22,140 --> 00:00:24,610 get to do it starting next week. 6 00:00:24,610 --> 00:00:27,530 So we are done for now talking about the essential oil lab, 7 00:00:27,530 --> 00:00:29,280 and you'll get one more lecture about that 8 00:00:29,280 --> 00:00:32,968 in the X-ray crystallography stuff coming up next week. 9 00:00:32,968 --> 00:00:35,010 And for now, we're going to switch gears and talk 10 00:00:35,010 --> 00:00:37,000 about the ester lab. 11 00:00:37,000 --> 00:00:39,625 So before we get too far into it, 12 00:00:39,625 --> 00:00:42,000 the Ellen Swallow Richards reports are due next Wednesday 13 00:00:42,000 --> 00:00:43,620 and Thursday, the 16th and 17th. 14 00:00:43,620 --> 00:00:45,610 The TAs will be holding office hours 15 00:00:45,610 --> 00:00:48,750 and I will post those onto Stellar this afternoon. 16 00:00:48,750 --> 00:00:50,842 And then starting this Wednesday and Thursday, 17 00:00:50,842 --> 00:00:52,800 we're going be starting our next round of labs, 18 00:00:52,800 --> 00:00:55,110 so wherever you are standing, whichever bay you're 19 00:00:55,110 --> 00:00:57,570 in in the lab, that will determine which lab 20 00:00:57,570 --> 00:00:58,845 you are going to do next. 21 00:00:58,845 --> 00:01:00,470 So A prime 2, center of the lab, you'll 22 00:01:00,470 --> 00:01:02,580 be doing essential oils, middle group, catalase, 23 00:01:02,580 --> 00:01:04,050 and then the people closest to the wall, 24 00:01:04,050 --> 00:01:05,550 you'll be doing the ester lab, which 25 00:01:05,550 --> 00:01:06,900 we're talking about today. 26 00:01:06,900 --> 00:01:08,850 If you're doing the catalase lab, and hopefully your TAs 27 00:01:08,850 --> 00:01:11,580 will remind you of this as well, but you need to bring a laptop. 28 00:01:11,580 --> 00:01:13,320 You'll be working in pairs, so if you don't have a laptop, 29 00:01:13,320 --> 00:01:15,403 then we can pair you up with somebody who has one. 30 00:01:15,403 --> 00:01:17,900 But we need a good number of laptops to do that. 31 00:01:17,900 --> 00:01:19,650 That's how you'll be collecting your data, 32 00:01:19,650 --> 00:01:23,590 and we'll talk more about that starting on Thursday. 33 00:01:23,590 --> 00:01:27,130 But moving on to esters, so the structure of an ester, 34 00:01:27,130 --> 00:01:28,840 which hopefully you guys have seen before 35 00:01:28,840 --> 00:01:31,300 in your organic chemistry or maybe your gen chem classes, 36 00:01:31,300 --> 00:01:32,720 is something like this. 37 00:01:32,720 --> 00:01:34,510 You have an R group where this first R 38 00:01:34,510 --> 00:01:37,240 group can be a hydrogen, any alkyl group 39 00:01:37,240 --> 00:01:39,430 or an aromatic group. 40 00:01:39,430 --> 00:01:41,950 Then you have your carbonyl, another oxygen and then 41 00:01:41,950 --> 00:01:44,800 a different R group. 42 00:01:44,800 --> 00:01:46,932 And this one can only be an alkyl or an aryl group. 43 00:01:46,932 --> 00:01:47,890 It has to have carbons. 44 00:01:47,890 --> 00:01:50,990 It can't be a hydrogen, or else you have a carboxylic acid. 45 00:01:50,990 --> 00:01:53,560 So that's the general structure of esters. 46 00:01:53,560 --> 00:01:56,290 And talking a little bit about background information 47 00:01:56,290 --> 00:01:59,560 about esters, they are found naturally in many plants, 48 00:01:59,560 --> 00:02:01,180 and you can synthesize them in the lab 49 00:02:01,180 --> 00:02:03,370 from carboxylic acids and alcohols, which 50 00:02:03,370 --> 00:02:04,780 we are going to be doing. 51 00:02:04,780 --> 00:02:07,660 They are highly fragrant, as you guys will experience 52 00:02:07,660 --> 00:02:10,610 when you do this lab, and so as such, 53 00:02:10,610 --> 00:02:13,570 they are used extensively in flavorings, scent and polymer 54 00:02:13,570 --> 00:02:14,110 industries. 55 00:02:14,110 --> 00:02:18,370 And so some esters that you may have seen before in the world, 56 00:02:18,370 --> 00:02:19,570 this is a triglyceride. 57 00:02:19,570 --> 00:02:21,100 This is how your body stores fats, 58 00:02:21,100 --> 00:02:23,630 and it makes it from glycerol, which is an alcohol.. 59 00:02:23,630 --> 00:02:26,370 It has three OH groups and a bunch of fatty acids. 60 00:02:26,370 --> 00:02:29,680 So that's one biological example of an ester that is very 61 00:02:29,680 --> 00:02:31,090 common in all of our bodies. 62 00:02:31,090 --> 00:02:33,940 And then this is ethyl cinnamate, 63 00:02:33,940 --> 00:02:36,820 which is an ester that is found in the essential oil 64 00:02:36,820 --> 00:02:39,820 of cinnamon, and it is what gives cinnamon 65 00:02:39,820 --> 00:02:43,800 its cinnamony flavor or scent. 66 00:02:43,800 --> 00:02:46,710 The most ubiquitous of esters is probably polyester. 67 00:02:46,710 --> 00:02:49,405 And so many of you are probably wearing polyester right now. 68 00:02:49,405 --> 00:02:50,280 It's in your fabrics. 69 00:02:50,280 --> 00:02:52,200 It's what plastic bottles are made out of. 70 00:02:52,200 --> 00:02:54,240 You have water bottles or food containers, 71 00:02:54,240 --> 00:02:55,470 all of these things. 72 00:02:55,470 --> 00:03:00,660 If you see this symbol that is the symbol for this plastic, 73 00:03:00,660 --> 00:03:02,820 which is the most common one used in our fabrics 74 00:03:02,820 --> 00:03:05,280 and in the food packaging that we have, 75 00:03:05,280 --> 00:03:07,620 and it is polyethylene terephthalate, 76 00:03:07,620 --> 00:03:09,190 and this is the structure. 77 00:03:09,190 --> 00:03:11,400 And so you can see that there is the ethylene group. 78 00:03:11,400 --> 00:03:13,050 There's the terephthalate group, and then there 79 00:03:13,050 --> 00:03:14,383 is our ester bond in the middle. 80 00:03:14,383 --> 00:03:16,950 And if so if you stack a lot of these together, 81 00:03:16,950 --> 00:03:20,940 you make a giant polymer, then you have all type of plastics 82 00:03:20,940 --> 00:03:25,108 that we use for many, many applications in our daily life. 83 00:03:25,108 --> 00:03:26,900 So a little bit of background about esters. 84 00:03:26,900 --> 00:03:30,358 And here's a chart of all of the different types of esters-- 85 00:03:30,358 --> 00:03:31,400 or not all of the esters. 86 00:03:31,400 --> 00:03:34,220 There's many, many, many types of esters that you can make, 87 00:03:34,220 --> 00:03:36,290 but here are some very common ones, especially 88 00:03:36,290 --> 00:03:38,570 ones that are found naturally in different food 89 00:03:38,570 --> 00:03:40,740 and natural products. 90 00:03:40,740 --> 00:03:44,450 So you can see there's the part from the carboxylic acid 91 00:03:44,450 --> 00:03:45,870 and the part from the alcohol. 92 00:03:45,870 --> 00:03:48,845 So if you make any of these combinations of esters, 93 00:03:48,845 --> 00:03:50,720 then they'll have all these different scents. 94 00:03:50,720 --> 00:03:52,490 And so in the lab, you guys are going 95 00:03:52,490 --> 00:03:54,320 to be synthesizing a whole bunch of different esters, 96 00:03:54,320 --> 00:03:56,487 and one of the ways that you may be able to identify 97 00:03:56,487 --> 00:03:57,925 it is by what it smells like. 98 00:03:57,925 --> 00:03:59,300 So if you look in the lab manual, 99 00:03:59,300 --> 00:04:00,410 there's a whole chart of the esters. 100 00:04:00,410 --> 00:04:01,410 It gives you their name. 101 00:04:01,410 --> 00:04:04,177 It gives you a bunch of physical information about it, 102 00:04:04,177 --> 00:04:05,510 and it also gives you the scent. 103 00:04:05,510 --> 00:04:07,670 So when you synthesize your ester, 104 00:04:07,670 --> 00:04:10,220 you will carefully smell it and see 105 00:04:10,220 --> 00:04:13,450 if it matches up to what it is supposed to smell like. 106 00:04:13,450 --> 00:04:15,832 AUDIENCE: What are the boxes that say ethereal? 107 00:04:15,832 --> 00:04:16,790 SARAH HEWETT: Ethereal? 108 00:04:16,790 --> 00:04:19,147 That is kind of-- 109 00:04:19,147 --> 00:04:21,230 I've never smelled something that smells ethereal. 110 00:04:21,230 --> 00:04:23,450 Does anyone have a good description 111 00:04:23,450 --> 00:04:25,500 of what that may smell like? 112 00:04:25,500 --> 00:04:29,480 I think it doesn't have like a concrete scent. 113 00:04:29,480 --> 00:04:31,090 That's how I kind of interpret that. 114 00:04:31,090 --> 00:04:33,270 But you can see there are some that smell like vanilla, 115 00:04:33,270 --> 00:04:34,440 pineapples, different fruits. 116 00:04:34,440 --> 00:04:36,148 Those are ones that smell like balsamicy, 117 00:04:36,148 --> 00:04:39,980 like vinegar, coconut, all kinds of different things. 118 00:04:42,522 --> 00:04:44,230 So we're going to talk about the reaction 119 00:04:44,230 --> 00:04:45,438 that we're going to be doing. 120 00:04:45,438 --> 00:04:46,435 This is Emil Fischer. 121 00:04:46,435 --> 00:04:49,540 He is half of the team that is responsible for creating 122 00:04:49,540 --> 00:04:51,130 or inventing this reaction. 123 00:04:51,130 --> 00:04:54,130 I could not find a picture of the other guy. 124 00:04:54,130 --> 00:04:57,250 He won the Nobel Prize for chemistry in the early 1900s, 125 00:04:57,250 --> 00:05:00,070 and now it is typically just called a Fischer esterification 126 00:05:00,070 --> 00:05:01,010 reaction. 127 00:05:01,010 --> 00:05:03,760 So you take your carboxyl acid, your alcohol, some acid, 128 00:05:03,760 --> 00:05:05,885 and then you can synthesize an ester. 129 00:05:05,885 --> 00:05:07,510 And so we'll walk through the mechanism 130 00:05:07,510 --> 00:05:09,552 really quickly so that we know what is happening. 131 00:05:09,552 --> 00:05:11,020 And you guys have probably-- 132 00:05:11,020 --> 00:05:13,450 have you guys seen this in your organic chemistry classes? 133 00:05:13,450 --> 00:05:16,938 Yes, so this hopefully isn't too new. 134 00:05:16,938 --> 00:05:18,730 So you start off with your carboxylic acid. 135 00:05:18,730 --> 00:05:21,200 We're going to add a strong acid in our case, sulfuric acid, 136 00:05:21,200 --> 00:05:22,200 which is very corrosive. 137 00:05:22,200 --> 00:05:24,160 Be careful when you're handling it in the lab. 138 00:05:24,160 --> 00:05:25,422 That is our proton source. 139 00:05:25,422 --> 00:05:27,130 So the first thing that we're going to do 140 00:05:27,130 --> 00:05:29,707 is activate this carbonyl. 141 00:05:29,707 --> 00:05:30,540 We get our carbonyl. 142 00:05:30,540 --> 00:05:33,148 Now it has a proton and a positive charge on it, 143 00:05:33,148 --> 00:05:34,690 and we can draw a resonance structure 144 00:05:34,690 --> 00:05:38,410 where that positive charge gets put down on this carbon here. 145 00:05:38,410 --> 00:05:40,710 And when we do that, we have our alcohol. 146 00:05:40,710 --> 00:05:43,920 We can add our alcohol in, and these electrons 147 00:05:43,920 --> 00:05:47,940 can come up here and attack that positively charged carbon. 148 00:05:47,940 --> 00:05:52,400 We can add our alcohol group to our original molecule. 149 00:05:52,400 --> 00:05:54,010 So now we have this guy here, and now 150 00:05:54,010 --> 00:05:58,570 the positive charge is on this oxygen. 151 00:05:58,570 --> 00:06:03,660 And so we can lose a proton to get rid 152 00:06:03,660 --> 00:06:05,800 of that positive charge. 153 00:06:05,800 --> 00:06:10,590 So then we end up with a proton over here. 154 00:06:10,590 --> 00:06:12,730 That's an unfortunate proton. 155 00:06:12,730 --> 00:06:18,390 And now we have this structure here with our extra proton. 156 00:06:18,390 --> 00:06:23,120 We can protonate this oxygen up here 157 00:06:23,120 --> 00:06:25,850 and form this charged species. 158 00:06:25,850 --> 00:06:28,890 And now we have made positively charged water, 159 00:06:28,890 --> 00:06:35,340 and we know that water is a good leaving group. 160 00:06:35,340 --> 00:06:39,380 So we can leave and make water, and that 161 00:06:39,380 --> 00:06:43,340 is where the water comes from in our synthesis. 162 00:06:43,340 --> 00:06:45,655 And to kind of balance this whole thing out, 163 00:06:45,655 --> 00:06:47,780 you're also going to have these electrons come down 164 00:06:47,780 --> 00:06:51,150 and form a double bond to help drive that water out. 165 00:06:51,150 --> 00:06:52,830 So now we have a double bond here. 166 00:06:52,830 --> 00:06:54,990 It has a positive charge and a proton 167 00:06:54,990 --> 00:07:01,647 still on it, so we can have this proton leave as a proton. 168 00:07:01,647 --> 00:07:02,730 And we have made an ester. 169 00:07:06,538 --> 00:07:07,970 Tada. 170 00:07:07,970 --> 00:07:09,650 And then we've regenerated our acids, 171 00:07:09,650 --> 00:07:12,320 so that's why the sulfuric acid is our catalyst. 172 00:07:12,320 --> 00:07:15,343 So I guess we can leave this here for now. 173 00:07:15,343 --> 00:07:17,760 So that is the mechanism of the reaction, and like I said, 174 00:07:17,760 --> 00:07:18,800 you guys have probably seen that before. 175 00:07:18,800 --> 00:07:20,630 It's pretty straightforward, and so this is the reaction 176 00:07:20,630 --> 00:07:22,040 that we will be doing in the lab. 177 00:07:25,120 --> 00:07:26,980 Now we need to talk about naming esters, 178 00:07:26,980 --> 00:07:28,330 and there are a couple of conventions that 179 00:07:28,330 --> 00:07:29,560 are used when naming esters. 180 00:07:29,560 --> 00:07:30,727 There's a few ways to do it. 181 00:07:30,727 --> 00:07:33,610 So the first one is the IUPAC straightforward way 182 00:07:33,610 --> 00:07:36,703 to name esters, and you start with the part of the molecule 183 00:07:36,703 --> 00:07:37,870 that comes from the alcohol. 184 00:07:37,870 --> 00:07:40,390 So if you notice over here, the blue stuff 185 00:07:40,390 --> 00:07:42,310 came from the alcohol, and it ends up 186 00:07:42,310 --> 00:07:45,400 as this group that's attached to the oxygen, 187 00:07:45,400 --> 00:07:48,068 not on the carbonyl side of the molecule. 188 00:07:48,068 --> 00:07:49,360 So you're going to start there. 189 00:07:49,360 --> 00:07:51,490 You'll name it as though it's an alkyl group, so something that 190 00:07:51,490 --> 00:07:52,120 is attached. 191 00:07:52,120 --> 00:07:55,120 So it'll have that -yl ending, like methyl, ethyl, 192 00:07:55,120 --> 00:07:56,540 that kind of thing. 193 00:07:56,540 --> 00:07:58,450 So this is a propyl group. 194 00:07:58,450 --> 00:08:00,470 It has three carbons. 195 00:08:00,470 --> 00:08:04,880 The second step is to look at the other half of the molecule, 196 00:08:04,880 --> 00:08:07,940 and you want to name it as though it isn't just an alkane 197 00:08:07,940 --> 00:08:10,940 and count up all the carbons including this one attached 198 00:08:10,940 --> 00:08:11,735 to the carbonyl. 199 00:08:11,735 --> 00:08:13,610 So you have one, two, three carbons over here 200 00:08:13,610 --> 00:08:16,910 as well, so that would be propane. 201 00:08:16,910 --> 00:08:19,390 And then you want to drop the e off the end of the name 202 00:08:19,390 --> 00:08:22,450 and add -oate, So proponoate. 203 00:08:22,450 --> 00:08:24,790 So the IUPAC way to name this thing 204 00:08:24,790 --> 00:08:26,470 is then to combine the names. 205 00:08:26,470 --> 00:08:31,230 So you'll get propyl, proponoate. 206 00:08:31,230 --> 00:08:34,710 So clear enough? 207 00:08:34,710 --> 00:08:37,460 It gets a little bit tricky because chemists don't always 208 00:08:37,460 --> 00:08:40,200 use the IUPAC or traditional names for everything. 209 00:08:40,200 --> 00:08:42,590 There are some common names that get used and thrown 210 00:08:42,590 --> 00:08:46,140 around when people are talking about different chemicals. 211 00:08:46,140 --> 00:08:48,350 So does anybody know what this carboxylic acid is? 212 00:08:51,000 --> 00:08:53,100 Acetate or acetic acid. 213 00:08:53,100 --> 00:08:54,990 So acetic acid is what we typically call it. 214 00:08:54,990 --> 00:08:56,407 You'll hear it as an acetate group 215 00:08:56,407 --> 00:08:59,145 if you take off that proton. 216 00:08:59,145 --> 00:09:01,270 If you're going to name this according to the IUPAC 217 00:09:01,270 --> 00:09:03,728 convention that I just told you about, there's two carbons, 218 00:09:03,728 --> 00:09:07,210 so that's ethane, and you would call it ethanoic acid, 219 00:09:07,210 --> 00:09:11,260 but that's not commonly used. 220 00:09:11,260 --> 00:09:13,090 This alcohol is ethanol. 221 00:09:13,090 --> 00:09:16,500 So if you combine these two, what would we call that ester? 222 00:09:20,100 --> 00:09:23,520 Ethyl ethanoate, or you can use the common name 223 00:09:23,520 --> 00:09:26,940 and call it ethyl acetate, which you guys may have heard of 224 00:09:26,940 --> 00:09:30,160 or remember from the ferrocene lab. 225 00:09:30,160 --> 00:09:31,900 Yes. 226 00:09:31,900 --> 00:09:33,670 So there are a couple of different ways 227 00:09:33,670 --> 00:09:37,397 to name the esters, and there's a whole list of esters. 228 00:09:37,397 --> 00:09:38,980 If you guys have looked in the manual, 229 00:09:38,980 --> 00:09:41,438 there's a whole list of possible unknowns that you can have 230 00:09:41,438 --> 00:09:43,210 and that you can make in this lab, 231 00:09:43,210 --> 00:09:45,220 and they come from all different combinations 232 00:09:45,220 --> 00:09:47,860 of carboxylic acids and alcohols. 233 00:09:47,860 --> 00:09:51,850 And so in order for you guys to have some idea of what 234 00:09:51,850 --> 00:09:53,350 you may be making and the structures 235 00:09:53,350 --> 00:09:56,320 that you will be looking for when you are characterizing 236 00:09:56,320 --> 00:09:59,230 your esters that you make by different types 237 00:09:59,230 --> 00:10:01,600 of spectroscopy, we need to be able to name and draw 238 00:10:01,600 --> 00:10:02,120 the esters. 239 00:10:02,120 --> 00:10:06,550 So if you got this handout in the back, on one side, 240 00:10:06,550 --> 00:10:11,800 it has a sheet that has all of the common names 241 00:10:11,800 --> 00:10:17,210 for the structures that you may find in that list of esters 242 00:10:17,210 --> 00:10:19,460 that we'll be making in the lab. 243 00:10:19,460 --> 00:10:21,338 And then on the back, there is a blank chart. 244 00:10:21,338 --> 00:10:22,880 Mine's already filled in, but there's 245 00:10:22,880 --> 00:10:27,150 a blank chart that has a bunch of different ester names. 246 00:10:27,150 --> 00:10:29,930 So if we want to take a moment and practice naming 247 00:10:29,930 --> 00:10:32,450 these esters using the information in the past two 248 00:10:32,450 --> 00:10:35,420 slides you should have on your PowerPoint handout 249 00:10:35,420 --> 00:10:39,250 and the structures on the back of here, 250 00:10:39,250 --> 00:10:42,010 you should be able to draw the structures of all 251 00:10:42,010 --> 00:10:44,350 of these different esters. 252 00:10:44,350 --> 00:10:47,020 So take a moment do that and talk with your neighbors. 253 00:10:47,020 --> 00:10:48,150 Work it out. 254 00:10:48,150 --> 00:10:50,590 Ask your TAs if you're back there. 255 00:10:50,590 --> 00:10:52,420 And then I'm going to have people, 256 00:10:52,420 --> 00:10:54,112 when you are confident that you know 257 00:10:54,112 --> 00:10:55,570 the structure of one of these guys, 258 00:10:55,570 --> 00:10:58,760 come down here and draw it please. 259 00:10:58,760 --> 00:11:02,263 So I'll give you a couple of minutes to do that. 260 00:11:02,263 --> 00:11:04,180 All right, can I get a few people to come help 261 00:11:04,180 --> 00:11:06,790 draw some of these on the board if you have drawn 262 00:11:06,790 --> 00:11:09,040 some of these on your paper? 263 00:11:09,040 --> 00:11:09,673 Go for it. 264 00:11:09,673 --> 00:11:11,590 Going to need a few other people, or else this 265 00:11:11,590 --> 00:11:12,632 is going to take forever. 266 00:11:15,680 --> 00:11:17,270 Excellent. 267 00:11:17,270 --> 00:11:18,195 Wonderful. 268 00:11:18,195 --> 00:11:19,820 Anyone from the back want to come down? 269 00:11:19,820 --> 00:11:20,280 Go for it. 270 00:11:20,280 --> 00:11:20,810 Thank you. 271 00:11:23,654 --> 00:11:25,273 AUDIENCE: [INAUDIBLE]. 272 00:11:25,273 --> 00:11:26,940 SARAH HEWETT: Don't worry if it's wrong. 273 00:11:32,375 --> 00:11:34,250 If you want to draw more than one, go for it. 274 00:11:34,250 --> 00:11:36,667 If anyone else wants to come down here and be really brave 275 00:11:36,667 --> 00:11:38,837 and share their knowledge, that would be excellent. 276 00:11:41,520 --> 00:11:45,960 All right, we'll see how many of them these guys can do. 277 00:11:45,960 --> 00:11:49,550 Yeah, if more than one, go for it because it'll be faster. 278 00:12:00,682 --> 00:12:01,768 AUDIENCE: [INAUDIBLE]. 279 00:12:01,768 --> 00:12:03,310 SARAH HEWETT: Yeah, sorry about that. 280 00:12:05,840 --> 00:12:06,410 One more. 281 00:12:23,820 --> 00:12:25,665 All right, how are we looking? 282 00:12:30,020 --> 00:12:34,381 Good, except this one, I think, these are the same molecule. 283 00:12:34,381 --> 00:12:35,303 AUDIENCE: [INAUDIBLE]. 284 00:12:38,530 --> 00:12:47,010 SARAH HEWETT: So butyl acetate, it's just no double bond. 285 00:12:47,010 --> 00:12:47,880 Thank you. 286 00:12:47,880 --> 00:12:50,480 Well done. 287 00:12:50,480 --> 00:12:53,680 So there are the structures of some of the esters 288 00:12:53,680 --> 00:12:57,700 that you may or may not be making during this lab. 289 00:12:57,700 --> 00:12:58,610 It's good practice. 290 00:12:58,610 --> 00:13:00,850 So these aren't all of them, so you'll still 291 00:13:00,850 --> 00:13:03,220 have to draw out some of the possible structures 292 00:13:03,220 --> 00:13:06,130 when you are trying to figure out what your unknown might be, 293 00:13:06,130 --> 00:13:08,270 but this is a good start and good practice. 294 00:13:08,270 --> 00:13:11,670 So it looks like you guys are good at drawing the esters. 295 00:13:11,670 --> 00:13:14,510 Well done. 296 00:13:14,510 --> 00:13:16,750 All right, so now that we have the idea of what 297 00:13:16,750 --> 00:13:19,853 the reaction looks like on paper and what our products could 298 00:13:19,853 --> 00:13:22,270 possibly be, we're going to talk about how we can actually 299 00:13:22,270 --> 00:13:23,720 do this in the lab. 300 00:13:23,720 --> 00:13:25,900 And so I brought some of the glassware 301 00:13:25,900 --> 00:13:27,150 that you're going to be using. 302 00:13:27,150 --> 00:13:29,350 And I'm going to put gloves on because I 303 00:13:29,350 --> 00:13:33,783 don't know how well whoever used this last semester cleaned it. 304 00:13:33,783 --> 00:13:36,200 So the first technique that you're going to use is reflux, 305 00:13:36,200 --> 00:13:38,545 and so that's to do the first part of, or pretty much 306 00:13:38,545 --> 00:13:39,920 do the whole reaction here, where 307 00:13:39,920 --> 00:13:42,050 you're going to combine your carboxylic acid 308 00:13:42,050 --> 00:13:43,160 and your alcohol. 309 00:13:43,160 --> 00:13:46,880 You're going to heat it up, and to reflux means to boil 310 00:13:46,880 --> 00:13:47,940 without losing solvents. 311 00:13:47,940 --> 00:13:49,400 So it'll be boiling. 312 00:13:49,400 --> 00:13:50,900 You'll have a stir bar in there. 313 00:13:50,900 --> 00:13:53,260 So you can see you have your stir plate. 314 00:13:53,260 --> 00:13:55,010 You're going to use a heating mantle again 315 00:13:55,010 --> 00:13:56,690 to heat your reaction. 316 00:13:56,690 --> 00:13:59,940 It'll be boiling in there, and then 317 00:13:59,940 --> 00:14:02,965 instead of using our Vigreux column 318 00:14:02,965 --> 00:14:04,590 like we did in the distillation, you're 319 00:14:04,590 --> 00:14:11,267 just going to put a condenser on there. 320 00:14:11,267 --> 00:14:13,350 So you'll have water going through your condenser. 321 00:14:13,350 --> 00:14:15,430 You'll want your water going in the bottom and out the top 322 00:14:15,430 --> 00:14:17,400 so that the whole thing fills up with cold water, 323 00:14:17,400 --> 00:14:18,600 and so that's when you're boiling. 324 00:14:18,600 --> 00:14:20,010 Your solvent will be evaporating, 325 00:14:20,010 --> 00:14:21,000 and then it'll condense and it'll 326 00:14:21,000 --> 00:14:22,917 go back down so that you don't boil to dryness 327 00:14:22,917 --> 00:14:26,350 and you don't lose all of your product as you're boiling it. 328 00:14:26,350 --> 00:14:29,392 And then on the top, you're going to put a drying tube, 329 00:14:29,392 --> 00:14:31,100 and your drying tube will look like this. 330 00:14:31,100 --> 00:14:33,600 And when you get it, it will be empty just like this one is, 331 00:14:33,600 --> 00:14:34,923 and then you will fill it. 332 00:14:34,923 --> 00:14:37,090 You'll put a little bit of cotton in here as a plug, 333 00:14:37,090 --> 00:14:39,465 and then you will take this stopper off and fill the rest 334 00:14:39,465 --> 00:14:42,010 of it with calcium chloride. 335 00:14:42,010 --> 00:14:44,930 Does anyone know why we're going to do that? 336 00:14:44,930 --> 00:14:46,180 And it goes right on top here. 337 00:14:51,330 --> 00:14:54,300 So calcium chloride is CaCl2. 338 00:14:54,300 --> 00:14:56,732 It is among other things used as a road salt. 339 00:14:56,732 --> 00:14:58,440 So there are three ions in the structure, 340 00:14:58,440 --> 00:15:00,090 and if you remember your colligative properties, 341 00:15:00,090 --> 00:15:02,100 then it'll lower the freezing point of water 342 00:15:02,100 --> 00:15:03,615 when it has three ions in it. 343 00:15:03,615 --> 00:15:05,460 It's a very good electrolyte. 344 00:15:05,460 --> 00:15:07,770 It'll also lower the vapor pressure of a solution 345 00:15:07,770 --> 00:15:10,200 or increase the boiling point. 346 00:15:10,200 --> 00:15:12,840 And the dissolution of calcium chloride is exothermic. 347 00:15:12,840 --> 00:15:14,910 It's very thermodynamically favorable 348 00:15:14,910 --> 00:15:16,740 and it's also entropically favorable, 349 00:15:16,740 --> 00:15:18,690 so it is a very spontaneous reaction, 350 00:15:18,690 --> 00:15:21,900 and it is a hygroscopic material, which 351 00:15:21,900 --> 00:15:23,287 means that it absorbs water. 352 00:15:23,287 --> 00:15:24,120 So it's a desiccant. 353 00:15:24,120 --> 00:15:25,890 You may see those like silica gel packets 354 00:15:25,890 --> 00:15:29,340 in things that you may buy to keep the water out. 355 00:15:29,340 --> 00:15:31,590 Calcium chloride is another material that's commonly 356 00:15:31,590 --> 00:15:34,080 used as a desiccant because it's hygroscopic, 357 00:15:34,080 --> 00:15:37,380 but it has a property even beyond being hygroscopic. 358 00:15:37,380 --> 00:15:39,840 It is deliquescent, which means it'll absorb water 359 00:15:39,840 --> 00:15:41,140 until it becomes a solution. 360 00:15:41,140 --> 00:15:44,500 So this is what dry calcium chloride pellets look like. 361 00:15:44,500 --> 00:15:46,877 So it's just little white chunks of solid. 362 00:15:46,877 --> 00:15:49,210 And if you leave it out on the benchtop for long enough, 363 00:15:49,210 --> 00:15:51,570 it'll actually pull in the water from the air 364 00:15:51,570 --> 00:15:55,580 and turn itself into a calcium chloride brine solution. 365 00:15:55,580 --> 00:15:57,485 So if you spill some of this on the bench, 366 00:15:57,485 --> 00:15:59,110 you want to clean it up really quickly, 367 00:15:59,110 --> 00:16:02,915 or else it will start to look like that. 368 00:16:02,915 --> 00:16:04,290 And so what we're going to use it 369 00:16:04,290 --> 00:16:06,912 for in our reaction is-- what are 370 00:16:06,912 --> 00:16:08,120 the products of our reaction? 371 00:16:08,120 --> 00:16:09,495 We're going to make an ester and? 372 00:16:12,790 --> 00:16:15,210 Water. 373 00:16:15,210 --> 00:16:17,770 So if we go back to our mechanism, we lose water here. 374 00:16:17,770 --> 00:16:20,010 And if you notice, most of these steps 375 00:16:20,010 --> 00:16:22,330 here are reversible steps. 376 00:16:22,330 --> 00:16:25,350 So if you remember Le Chatelier's principle, 377 00:16:25,350 --> 00:16:27,750 if this is our overall reaction and one 378 00:16:27,750 --> 00:16:33,050 of our products over here is water, 379 00:16:33,050 --> 00:16:35,540 and this is a reversible reaction, 380 00:16:35,540 --> 00:16:38,180 then how can we force the reaction 381 00:16:38,180 --> 00:16:40,810 to go towards the product side? 382 00:16:40,810 --> 00:16:42,070 AUDIENCE: Take out the water. 383 00:16:42,070 --> 00:16:42,680 SARAH HEWETT: Take out the water. 384 00:16:42,680 --> 00:16:43,720 You can either add more reactants 385 00:16:43,720 --> 00:16:45,213 or take out the products, and so we 386 00:16:45,213 --> 00:16:47,630 are going to be taking out the water with our drying tube. 387 00:16:47,630 --> 00:16:50,650 And so that will help ensure that our reaction goes 388 00:16:50,650 --> 00:16:54,890 to completion while we are refluxing. 389 00:16:54,890 --> 00:16:57,080 So once you've done all of your reflux 390 00:16:57,080 --> 00:16:59,720 and you have your product, you've heated it for a while-- 391 00:16:59,720 --> 00:17:02,593 it's kind of boring to watch, but reactions take time-- 392 00:17:02,593 --> 00:17:04,010 so then you will have your product 393 00:17:04,010 --> 00:17:06,420 in your round-bottom flask here. 394 00:17:06,420 --> 00:17:10,500 And we will have our ester, hopefully, and what else? 395 00:17:13,280 --> 00:17:16,339 Potentially all of these things, right, and some sulfuric acid. 396 00:17:16,339 --> 00:17:18,589 So we don't know that our reaction went to completion. 397 00:17:18,589 --> 00:17:20,060 We hope that it got close, but we 398 00:17:20,060 --> 00:17:23,030 need to purify it from any impurities or remaining 399 00:17:23,030 --> 00:17:24,630 starting material that we may have. 400 00:17:24,630 --> 00:17:26,690 So we do that in a separatory funnel, 401 00:17:26,690 --> 00:17:29,240 and this is a separatory funnel. 402 00:17:29,240 --> 00:17:30,810 And we do a liquid-liquid extraction, 403 00:17:30,810 --> 00:17:32,810 which means that we're going to have one liquid, 404 00:17:32,810 --> 00:17:34,380 and then we're going to add a different liquid to it. 405 00:17:34,380 --> 00:17:35,750 So we have two liquid phases, and we're 406 00:17:35,750 --> 00:17:38,420 going to partition the different compounds between those two 407 00:17:38,420 --> 00:17:40,150 liquid phases. 408 00:17:40,150 --> 00:17:41,950 And the only way this works is that we 409 00:17:41,950 --> 00:17:44,410 have to have two immiscible liquids that 410 00:17:44,410 --> 00:17:45,470 have different densities. 411 00:17:45,470 --> 00:17:47,880 So what does it mean for something to be immiscible? 412 00:17:52,693 --> 00:17:54,110 AUDIENCE: They won't mix together. 413 00:17:54,110 --> 00:17:55,205 SARAH HEWETT: They don't mix together. 414 00:17:55,205 --> 00:17:55,705 Good. 415 00:17:55,705 --> 00:17:57,920 So when you pour your two solvents in here, 416 00:17:57,920 --> 00:18:01,290 they need to not mix so that have two distinct layers 417 00:18:01,290 --> 00:18:03,938 and that you can separate your product between them. 418 00:18:03,938 --> 00:18:05,730 And it will separate them based on density. 419 00:18:05,730 --> 00:18:07,040 So when you have your separatory funnel, 420 00:18:07,040 --> 00:18:08,660 you will pour your two things into it, 421 00:18:08,660 --> 00:18:10,160 and you should get two layers. 422 00:18:10,160 --> 00:18:12,980 And so your more dense layer will be on the bottom 423 00:18:12,980 --> 00:18:15,960 and your less dense layer will be on the top. 424 00:18:15,960 --> 00:18:19,700 So in our case, water has a density of about 1 425 00:18:19,700 --> 00:18:23,520 and most organic liquids have a density of less than 1. 426 00:18:23,520 --> 00:18:28,190 So if you take your product, which is an ester, 427 00:18:28,190 --> 00:18:30,408 and you add water to it, what will be on the top 428 00:18:30,408 --> 00:18:31,700 and what will be on the bottom? 429 00:18:34,580 --> 00:18:36,330 AUDIENCE: The water will be on the bottom. 430 00:18:36,330 --> 00:18:37,080 SARAH HEWETT: Yep. 431 00:18:37,080 --> 00:18:40,900 So this will be our aqueous layer 432 00:18:40,900 --> 00:18:43,180 and this will be our product or our organic layer. 433 00:18:47,693 --> 00:18:49,110 And it's really important that you 434 00:18:49,110 --> 00:18:51,090 keep track of what is where when you're 435 00:18:51,090 --> 00:18:53,100 using the separatory funnel and that you 436 00:18:53,100 --> 00:18:56,280 know what you've drained out and what you have kept in there. 437 00:18:56,280 --> 00:18:57,630 And you want to save everything. 438 00:18:57,630 --> 00:18:59,310 Save all of the stuff that comes out of here. 439 00:18:59,310 --> 00:19:01,477 Save all the things that are in there until you know 440 00:19:01,477 --> 00:19:03,088 that you have your product. 441 00:19:03,088 --> 00:19:04,630 So there are a couple of ways that we 442 00:19:04,630 --> 00:19:07,780 can use a separatory funnel or as a sep funnel, 443 00:19:07,780 --> 00:19:09,520 the abbreviated version. 444 00:19:09,520 --> 00:19:11,560 And the frequently used solutions 445 00:19:11,560 --> 00:19:13,600 for this type of extraction, the first type 446 00:19:13,600 --> 00:19:16,575 is an acid-base extraction or a chemically active extraction, 447 00:19:16,575 --> 00:19:18,950 and that's the first thing that you're going to be doing. 448 00:19:18,950 --> 00:19:22,180 So in our reaction mixture, we have 449 00:19:22,180 --> 00:19:24,070 hopefully a lot of product. 450 00:19:24,070 --> 00:19:26,522 We probably still have some carboxylic acid left over, 451 00:19:26,522 --> 00:19:28,730 and we know that we have some sulfuric acid in there. 452 00:19:28,730 --> 00:19:30,430 Yes? 453 00:19:30,430 --> 00:19:32,020 Great. 454 00:19:32,020 --> 00:19:35,020 So the way to get all of that acidic byproduct 455 00:19:35,020 --> 00:19:39,190 away from our product is to use sodium bicarbonate, which 456 00:19:39,190 --> 00:19:40,550 is a base. 457 00:19:40,550 --> 00:19:41,680 And when we do that-- 458 00:19:44,360 --> 00:19:51,930 so if we have our carboxylic acid, if you add a base to it, 459 00:19:51,930 --> 00:19:57,690 then you can deprotonate it, and if we have sodium bicarbonate, 460 00:19:57,690 --> 00:20:02,800 it will form a sodium salt. And that is more polar than this, 461 00:20:02,800 --> 00:20:06,030 so it will be more soluble in our aqueous layer, 462 00:20:06,030 --> 00:20:08,930 and we will pull it away from our product. 463 00:20:08,930 --> 00:20:13,820 So that's the idea behind the base extraction. 464 00:20:13,820 --> 00:20:16,160 And so hopefully, that first round of extraction 465 00:20:16,160 --> 00:20:18,380 will get rid of our acidic impurities, 466 00:20:18,380 --> 00:20:22,645 and then we're going to do another extraction using 467 00:20:22,645 --> 00:20:24,620 a sodium chloride solution. 468 00:20:24,620 --> 00:20:27,140 And that is sometimes referred to as salting out. 469 00:20:27,140 --> 00:20:29,033 So we will keep our product in there, 470 00:20:29,033 --> 00:20:30,950 and then we will add sodium chloride solution. 471 00:20:30,950 --> 00:20:34,940 And the sodium chloride makes our aqueous layer really polar, 472 00:20:34,940 --> 00:20:39,830 and so it makes our product less soluble in the aqueous layer, 473 00:20:39,830 --> 00:20:44,610 and it makes any water that's left over in our product layer 474 00:20:44,610 --> 00:20:46,403 more likely to come into the aqueous layer. 475 00:20:46,403 --> 00:20:48,570 So when this is polar, than all of the polar things, 476 00:20:48,570 --> 00:20:51,745 all of the water, get pulled into the aqueous layer, 477 00:20:51,745 --> 00:20:54,120 and any organic-y things, the product that we care about, 478 00:20:54,120 --> 00:20:58,445 gets forced out into the product layer. 479 00:20:58,445 --> 00:20:59,820 There's some terminology that you 480 00:20:59,820 --> 00:21:01,820 may hear when you are using a separatory funnel. 481 00:21:01,820 --> 00:21:03,930 So there's extraction, which is if your product is 482 00:21:03,930 --> 00:21:05,388 in a mixture and you to add another 483 00:21:05,388 --> 00:21:08,700 solvent to extract your product out of what's already there. 484 00:21:08,700 --> 00:21:11,260 And then there's washing, which is we're going to be doing, 485 00:21:11,260 --> 00:21:12,900 which is where you're just going to pour your product in there 486 00:21:12,900 --> 00:21:14,525 and you are going to add other solvents 487 00:21:14,525 --> 00:21:15,660 to extract the impurities. 488 00:21:15,660 --> 00:21:17,077 You leave your product where it is 489 00:21:17,077 --> 00:21:20,073 and you pull out the impurities. 490 00:21:20,073 --> 00:21:21,490 A note on how to use a sep funnel, 491 00:21:21,490 --> 00:21:25,058 and I'm going to put goggles on just for safety here. 492 00:21:25,058 --> 00:21:26,850 This is just water, but the way that you're 493 00:21:26,850 --> 00:21:28,800 going to do this is you'll have a ring stand. 494 00:21:28,800 --> 00:21:31,290 It'll hold itself up right here, and then you 495 00:21:31,290 --> 00:21:34,223 will first make sure that the stopcock is closed. 496 00:21:34,223 --> 00:21:36,640 So if you pour your product through here and this is open, 497 00:21:36,640 --> 00:21:39,253 then that's going to be a really sad time in the lab. 498 00:21:39,253 --> 00:21:41,920 So then you'll pour your product and whatever you are washing it 499 00:21:41,920 --> 00:21:43,848 with into the sep funnel. 500 00:21:43,848 --> 00:21:45,640 You will get two layers because you'll have 501 00:21:45,640 --> 00:21:46,700 two different liquids in there. 502 00:21:46,700 --> 00:21:47,555 This is just water. 503 00:21:47,555 --> 00:21:48,430 Then you will cap it. 504 00:21:50,950 --> 00:21:53,300 And then you're going to shake it like so. 505 00:21:53,300 --> 00:21:56,350 Then you will point it away from any humans and into your hood 506 00:21:56,350 --> 00:21:59,180 and you will open the vent. 507 00:21:59,180 --> 00:22:02,840 When you are shaking things that have are really 508 00:22:02,840 --> 00:22:04,550 volatile like organic solvents, they'll 509 00:22:04,550 --> 00:22:06,170 build up pressure in here, and so you 510 00:22:06,170 --> 00:22:07,550 don't want anything to explode. 511 00:22:07,550 --> 00:22:09,342 You don't want this top to come flying off. 512 00:22:09,342 --> 00:22:11,450 You don't want the glassware to break. 513 00:22:11,450 --> 00:22:12,890 So you want to vent this. 514 00:22:12,890 --> 00:22:15,140 You're going to shake it a little bit, vent it. 515 00:22:15,140 --> 00:22:16,430 When you first start, you want to vent it 516 00:22:16,430 --> 00:22:18,080 very frequently so that the pressure doesn't have a chance 517 00:22:18,080 --> 00:22:18,688 to build up. 518 00:22:18,688 --> 00:22:20,480 When you do this, you want to point it away 519 00:22:20,480 --> 00:22:22,445 because sometimes, liquid will come flying out. 520 00:22:22,445 --> 00:22:23,070 You'll hear it. 521 00:22:23,070 --> 00:22:25,160 It'll go pssh. 522 00:22:25,160 --> 00:22:28,330 So you want to be very careful when you are using this. 523 00:22:28,330 --> 00:22:31,700 Safety note. 524 00:22:31,700 --> 00:22:35,720 What happens when you add sodium bicarbonate to an acid? 525 00:22:35,720 --> 00:22:36,620 You get a gas. 526 00:22:36,620 --> 00:22:37,850 You get carbon dioxide. 527 00:22:37,850 --> 00:22:41,450 Think baking soda and vinegar volcano. 528 00:22:41,450 --> 00:22:44,420 So when you are first adding your sodium bicarbonate 529 00:22:44,420 --> 00:22:46,580 to your product, you want to not do it 530 00:22:46,580 --> 00:22:48,080 right away in the separatory funnel, 531 00:22:48,080 --> 00:22:49,740 or else you're going to build up a whole lot of pressure, 532 00:22:49,740 --> 00:22:51,930 and it's going to create an unsafe situation. 533 00:22:51,930 --> 00:22:53,900 So you will add those to a beaker first. 534 00:22:53,900 --> 00:22:56,510 Wait for the bubbling to stop, and then you 535 00:22:56,510 --> 00:22:58,310 can pour it into your separatory funnel 536 00:22:58,310 --> 00:22:59,870 and you can do the extraction. 537 00:22:59,870 --> 00:23:03,320 And what you're going to do is you will open the stopcock, 538 00:23:03,320 --> 00:23:05,600 and then you'll be able to watch the layers go down. 539 00:23:05,600 --> 00:23:06,800 And here's something. 540 00:23:06,800 --> 00:23:09,150 So if you open the stopcock and you say, 541 00:23:09,150 --> 00:23:13,400 oh my gosh, nothing's coming out, what's our problem? 542 00:23:13,400 --> 00:23:14,820 The top is on. 543 00:23:14,820 --> 00:23:16,070 So you want to close it first. 544 00:23:16,070 --> 00:23:19,442 Take the top off and then it will drain smoothly. 545 00:23:19,442 --> 00:23:20,900 And then you'll just pay attention, 546 00:23:20,900 --> 00:23:23,728 and you can stop it right when the interface between those two 547 00:23:23,728 --> 00:23:25,520 layers gets right to the bottom, and that's 548 00:23:25,520 --> 00:23:28,718 how you're going to use this to separate your solutions. 549 00:23:28,718 --> 00:23:30,260 But yeah, inevitably, somebody always 550 00:23:30,260 --> 00:23:31,460 forgets to take the top off, and they're like, 551 00:23:31,460 --> 00:23:32,420 my sep funnel's broken. 552 00:23:32,420 --> 00:23:34,430 It's not. 553 00:23:34,430 --> 00:23:36,090 Just physics. 554 00:23:36,090 --> 00:23:39,918 So I guess we can still leave these on. 555 00:23:39,918 --> 00:23:41,460 So that's going to be all in day one. 556 00:23:41,460 --> 00:23:42,773 You will reflux your product. 557 00:23:42,773 --> 00:23:44,190 Then you will use your sep funnel. 558 00:23:44,190 --> 00:23:46,170 You will start to purify it, and then on day two, 559 00:23:46,170 --> 00:23:46,710 you're going to-- 560 00:23:46,710 --> 00:23:47,220 Oh, wait. 561 00:23:47,220 --> 00:23:49,530 Before, sorry. 562 00:23:49,530 --> 00:23:51,197 So after you have isolated your product, 563 00:23:51,197 --> 00:23:53,488 we have just added a whole bunch of water to it, right. 564 00:23:53,488 --> 00:23:56,190 We've shaken it up with sodium bicarbonate and sodium chloride 565 00:23:56,190 --> 00:23:57,930 solution. 566 00:23:57,930 --> 00:23:59,392 We don't want water in our product. 567 00:23:59,392 --> 00:24:00,600 That's not the point of this. 568 00:24:00,600 --> 00:24:02,400 We want to just have our ester, so we 569 00:24:02,400 --> 00:24:04,560 need to remove the water that gets left over 570 00:24:04,560 --> 00:24:07,770 from our separatory funnel situation using a drying agent, 571 00:24:07,770 --> 00:24:10,260 and a drying agent is similar to calcium chloride. 572 00:24:10,260 --> 00:24:13,140 We typically use sodium sulfate or magnesium sulfate in the lab 573 00:24:13,140 --> 00:24:15,790 because they're easy to work with 574 00:24:15,790 --> 00:24:18,190 and they suck the water into their crystal lattice, 575 00:24:18,190 --> 00:24:22,080 and they necessarily dissolve very well, which is nice. 576 00:24:22,080 --> 00:24:23,910 And so these are fairly interchangeable. 577 00:24:23,910 --> 00:24:26,217 They're the most commonly ones used in lab situations. 578 00:24:26,217 --> 00:24:28,800 Magnesium sulfate sometimes can harm acid-sensitive compounds, 579 00:24:28,800 --> 00:24:30,480 so if you're doing something very sensitive in the lab, 580 00:24:30,480 --> 00:24:32,230 you may want to stick with sodium sulfate, 581 00:24:32,230 --> 00:24:34,590 but for our purposes, it will be fine. 582 00:24:34,590 --> 00:24:36,840 So what you're going to do is it comes in powder form, 583 00:24:36,840 --> 00:24:38,632 and you will add some of it to your product 584 00:24:38,632 --> 00:24:39,985 and you will swirl it around. 585 00:24:39,985 --> 00:24:42,360 And you will look at it, and then you will run to your TA 586 00:24:42,360 --> 00:24:45,300 and say something like this, like, ah, is it dry yet. 587 00:24:45,300 --> 00:24:46,140 How much do I add? 588 00:24:46,140 --> 00:24:48,750 And your TA will look at you and say, I don't know. 589 00:24:48,750 --> 00:24:50,350 You should know this. 590 00:24:50,350 --> 00:24:53,470 So this is how you could tell if it is dry yet. 591 00:24:53,470 --> 00:24:56,943 The first time that you add your drying agent, it will clump up 592 00:24:56,943 --> 00:24:58,360 and it'll all be in one big chunk, 593 00:24:58,360 --> 00:24:59,770 especially if you have a lot of water in there. 594 00:24:59,770 --> 00:25:01,470 Sometimes you can even see the water. 595 00:25:01,470 --> 00:25:02,440 If you hold up your flask, you'll 596 00:25:02,440 --> 00:25:04,690 be able to see a little bubble of water at the bottom. 597 00:25:04,690 --> 00:25:05,380 That's fine. 598 00:25:05,380 --> 00:25:06,250 You'll add your drying agent. 599 00:25:06,250 --> 00:25:07,030 It'll all clump up. 600 00:25:07,030 --> 00:25:08,238 You'll add a little bit more. 601 00:25:08,238 --> 00:25:10,420 It'll have some smaller clumps, and then you'll 602 00:25:10,420 --> 00:25:12,070 add a tiny scoop more. 603 00:25:12,070 --> 00:25:14,338 And the rest of it that you add won't clump up. 604 00:25:14,338 --> 00:25:15,880 It'll look kind of like a snow globe. 605 00:25:15,880 --> 00:25:17,880 It'll swirl around and be free-flowing crystals, 606 00:25:17,880 --> 00:25:19,900 and that is how you know when you are done, when 607 00:25:19,900 --> 00:25:21,950 it doesn't clump up anymore. 608 00:25:21,950 --> 00:25:24,105 So you don't need to go over and weigh it. 609 00:25:24,105 --> 00:25:26,480 I think there's an approximate weight in your lab manual. 610 00:25:26,480 --> 00:25:28,612 Like usually, it's maybe around a gram. 611 00:25:28,612 --> 00:25:30,070 But don't bother weighing this out. 612 00:25:30,070 --> 00:25:32,520 You can just kind of eyeball it, scooping a little bit 613 00:25:32,520 --> 00:25:33,020 at a time. 614 00:25:33,020 --> 00:25:35,698 Don't go too crazy with the first scoop, 615 00:25:35,698 --> 00:25:37,990 because the more of this that you have in your product, 616 00:25:37,990 --> 00:25:40,845 the harder it will be to isolate your product later. 617 00:25:40,845 --> 00:25:42,970 So let's say, if you think of it like at the beach, 618 00:25:42,970 --> 00:25:45,512 if you have a bunch of sand and then you put a bunch of water 619 00:25:45,512 --> 00:25:47,200 in it, your water kind of disappears. 620 00:25:47,200 --> 00:25:49,180 And in this case, our product is the liquid, 621 00:25:49,180 --> 00:25:50,680 so in order to get our product back, 622 00:25:50,680 --> 00:25:53,110 we will gravity-filter this away from the drying agent. 623 00:25:53,110 --> 00:25:55,690 And so you want to have minimal amount of drying agent 624 00:25:55,690 --> 00:25:57,523 so that your product doesn't get stuck in it 625 00:25:57,523 --> 00:26:00,240 and it's easy to filter later. 626 00:26:00,240 --> 00:26:02,760 OK, so that's all day one. 627 00:26:02,760 --> 00:26:05,370 Then you'll have your semi-purified and dried 628 00:26:05,370 --> 00:26:07,350 product, and then on day two, we will purify it 629 00:26:07,350 --> 00:26:10,200 from anything that did not get taken out in your extraction 630 00:26:10,200 --> 00:26:11,940 process using distillation. 631 00:26:11,940 --> 00:26:14,350 And what I didn't mention is that for this lab, 632 00:26:14,350 --> 00:26:16,350 you'll be checking out a kit from the stockroom, 633 00:26:16,350 --> 00:26:18,017 or your TAs will check this out, and you 634 00:26:18,017 --> 00:26:19,950 will get a kit that has all of the glassware 635 00:26:19,950 --> 00:26:21,658 that you need to do the entire lab in it. 636 00:26:21,658 --> 00:26:24,312 And there's a nice list on here of what goes in this kit. 637 00:26:24,312 --> 00:26:26,520 So on the first day, you will set up your reflux just 638 00:26:26,520 --> 00:26:28,320 like this, and then the second day, we're 639 00:26:28,320 --> 00:26:30,420 going to set up an atmospheric distillation, which 640 00:26:30,420 --> 00:26:32,670 is going to be very similar to the vacuum distillation 641 00:26:32,670 --> 00:26:34,300 that we talked about before. 642 00:26:34,300 --> 00:26:37,170 But this time, instead of having all the glassware in one piece, 643 00:26:37,170 --> 00:26:38,640 you get to assemble it yourself. 644 00:26:38,640 --> 00:26:41,890 So you'll have your Vigreux column. 645 00:26:41,890 --> 00:26:44,297 Then you'll have a distilling head up here, 646 00:26:44,297 --> 00:26:46,380 and then you will put your thermometer in the top. 647 00:26:46,380 --> 00:26:48,900 And most of our thermometers have ground glass joints. 648 00:26:48,900 --> 00:26:50,567 And then you will use the same condenser 649 00:26:50,567 --> 00:26:52,740 that you used for your reflux on day one, 650 00:26:52,740 --> 00:26:55,000 and that will go across like this. 651 00:26:55,000 --> 00:26:57,310 And you will clamp all of this glassware very well, 652 00:26:57,310 --> 00:27:01,800 and then you will add your spout to the end of it right here. 653 00:27:01,800 --> 00:27:05,180 And that is your distillation setup. 654 00:27:05,180 --> 00:27:08,210 You'll have keck clips in your lab, those yellow things that 655 00:27:08,210 --> 00:27:09,750 hold all of your joints together. 656 00:27:09,750 --> 00:27:10,670 So you want to make sure that everything 657 00:27:10,670 --> 00:27:12,920 is clamped and secure before you start distilling, 658 00:27:12,920 --> 00:27:15,093 because if you have gaps in your glassware 659 00:27:15,093 --> 00:27:17,510 and then you start heating and your product becomes a gas, 660 00:27:17,510 --> 00:27:19,460 you will lose it all. 661 00:27:19,460 --> 00:27:21,830 So the distillation will purify your product 662 00:27:21,830 --> 00:27:25,130 from any remaining insoluble impurities or higher 663 00:27:25,130 --> 00:27:29,480 boiling impurities that we do not want in our final product. 664 00:27:32,563 --> 00:27:33,980 And when you do this, you're going 665 00:27:33,980 --> 00:27:35,400 to collect a few different fractions. 666 00:27:35,400 --> 00:27:36,840 And so the way that you're going collect your fractions 667 00:27:36,840 --> 00:27:38,780 in this case, we don't need to use a cow adapter because we're 668 00:27:38,780 --> 00:27:41,308 not going to be attaching anything to the vacuum line. 669 00:27:41,308 --> 00:27:43,850 You can see that the spot over here, instead of attaching it, 670 00:27:43,850 --> 00:27:45,267 this is where you put your vacuum. 671 00:27:45,267 --> 00:27:46,380 It's just open to the air. 672 00:27:46,380 --> 00:27:49,273 And so you can collect your fractions in test tubes on ice, 673 00:27:49,273 --> 00:27:51,440 and then you will collect a few different fractions. 674 00:27:51,440 --> 00:27:53,607 So you usually collect the first few drops and then 675 00:27:53,607 --> 00:27:54,690 a few different fractions. 676 00:27:54,690 --> 00:27:56,300 If the temperature changes, you will switch your fractions, 677 00:27:56,300 --> 00:27:58,050 and your TAs will tell you how to do that. 678 00:27:58,050 --> 00:28:00,830 And then you will monitor your purity by IR. 679 00:28:00,830 --> 00:28:02,600 So if we go back and think about the IR 680 00:28:02,600 --> 00:28:06,050 that we talked about last time, and if we 681 00:28:06,050 --> 00:28:10,910 think about our products and our reactants, what IR bands 682 00:28:10,910 --> 00:28:14,540 are we going to see in our carboxylic acid reactant? 683 00:28:19,990 --> 00:28:31,550 We have a C-O stretch, an O-H C double-bond O. And? 684 00:28:31,550 --> 00:28:33,830 You might see the CC, you may not. 685 00:28:33,830 --> 00:28:35,472 Those ones are kind of hard to do 686 00:28:35,472 --> 00:28:37,430 because they don't change dipole very much when 687 00:28:37,430 --> 00:28:38,490 that bond happens. 688 00:28:38,490 --> 00:28:41,240 So sometimes, maybe a C-C bond. 689 00:28:41,240 --> 00:28:42,050 And what else? 690 00:28:42,050 --> 00:28:44,120 What's in this R group? 691 00:28:44,120 --> 00:28:47,372 Yeah, C-H stretches. 692 00:28:47,372 --> 00:28:48,580 What about our alcohol group? 693 00:28:52,480 --> 00:28:54,010 We'll have another OH stretch. 694 00:28:54,010 --> 00:28:59,570 Of we have a C single-bond O. Yep. 695 00:28:59,570 --> 00:29:00,820 Do we have one of these? 696 00:29:00,820 --> 00:29:02,410 No. 697 00:29:02,410 --> 00:29:03,035 None of those. 698 00:29:03,035 --> 00:29:03,910 We have some of this? 699 00:29:03,910 --> 00:29:04,940 AUDIENCE: Yeah. 700 00:29:04,940 --> 00:29:06,980 SARAH HEWETT: Yeah. 701 00:29:06,980 --> 00:29:08,810 And then again, maybe the C-C bonds, 702 00:29:08,810 --> 00:29:09,950 sometimes those are in the [INAUDIBLE] region. 703 00:29:09,950 --> 00:29:10,685 You probably won't. 704 00:29:10,685 --> 00:29:12,518 Don't spend too much time looking for these. 705 00:29:12,518 --> 00:29:16,560 These are kind of there but not easy to see. 706 00:29:16,560 --> 00:29:17,990 So now if we look at our product, 707 00:29:17,990 --> 00:29:20,313 what do we expect to be in our product, 708 00:29:20,313 --> 00:29:22,230 assuming we don't have any water because we've 709 00:29:22,230 --> 00:29:25,880 done our distillation and our extractions very well? 710 00:29:25,880 --> 00:29:38,080 We have a C double-bond O. A C single-bond O. A C-H. 711 00:29:38,080 --> 00:29:39,030 Do we have an O-H? 712 00:29:42,710 --> 00:29:44,460 So what are we going to look for in our IR 713 00:29:44,460 --> 00:29:47,390 to tell if we still have starting material in there 714 00:29:47,390 --> 00:29:48,176 or not? 715 00:29:48,176 --> 00:29:50,503 AUDIENCE: The O-H [INAUDIBLE]. 716 00:29:50,503 --> 00:29:51,920 SARAH HEWETT: The O-H. And so this 717 00:29:51,920 --> 00:29:54,253 will still have a C double-bond O, so that one might not 718 00:29:54,253 --> 00:29:56,780 be as easy to tell. 719 00:29:56,780 --> 00:29:59,690 But we definitely should not have an O-H peak. 720 00:29:59,690 --> 00:30:02,420 So if you take your Ir fractions and you take your fractions, 721 00:30:02,420 --> 00:30:03,920 you take the IR of them and then you 722 00:30:03,920 --> 00:30:06,460 start to see the O-H, the characteristic O-H peak 723 00:30:06,460 --> 00:30:10,043 up way by like 3,000 wave numbers, 724 00:30:10,043 --> 00:30:11,960 then you may want to test a different fraction 725 00:30:11,960 --> 00:30:13,793 because that one either has some water in it 726 00:30:13,793 --> 00:30:17,738 or it still has some of your starting material. 727 00:30:17,738 --> 00:30:20,030 And then once you've determined which of your fractions 728 00:30:20,030 --> 00:30:22,070 is the most pure, then you will continue on 729 00:30:22,070 --> 00:30:25,002 with that to do the rest of our characterization techniques. 730 00:30:25,002 --> 00:30:26,460 And the first one of those is going 731 00:30:26,460 --> 00:30:27,877 to be boiling point determination. 732 00:30:27,877 --> 00:30:31,368 So we can determine the boiling point of the ester, 733 00:30:31,368 --> 00:30:33,160 and that is a characteristic of each ester. 734 00:30:33,160 --> 00:30:34,020 So you have a chart. 735 00:30:34,020 --> 00:30:35,130 That chart at the beginning of the lab, 736 00:30:35,130 --> 00:30:36,825 it has a list of all the boiling points. 737 00:30:36,825 --> 00:30:38,385 So we will measure the boiling point of your ester, 738 00:30:38,385 --> 00:30:39,480 but before we do that, we're going 739 00:30:39,480 --> 00:30:41,700 to calibrate the thermometer just like we calibrated 740 00:30:41,700 --> 00:30:43,488 the melting point apparatus. 741 00:30:43,488 --> 00:30:45,780 So at this time, there are only two calibration points. 742 00:30:45,780 --> 00:30:47,942 So you'll measure the freezing point of water. 743 00:30:47,942 --> 00:30:48,900 So you'll get a beaker. 744 00:30:48,900 --> 00:30:51,480 You'll fill it up with ice, some water, 745 00:30:51,480 --> 00:30:53,463 let the temperature reach equilibrium. 746 00:30:53,463 --> 00:30:55,380 And you want make sure there's still ice in it 747 00:30:55,380 --> 00:30:57,005 when you measure so that it's not water 748 00:30:57,005 --> 00:30:59,580 and it's not heating back up to room temperature. 749 00:30:59,580 --> 00:31:00,630 And then you will measure the temperature 750 00:31:00,630 --> 00:31:02,005 of the very cold water after it's 751 00:31:02,005 --> 00:31:03,570 sat for about 10 to 15 minutes. 752 00:31:03,570 --> 00:31:07,770 While you're doing that, you can also heat up a beaker of water 753 00:31:07,770 --> 00:31:11,342 on a hot plate, measure it and heat it up to boiling, 754 00:31:11,342 --> 00:31:13,050 and then you will measure the temperature 755 00:31:13,050 --> 00:31:14,710 of the boiling water. 756 00:31:14,710 --> 00:31:16,910 And there's a correction factor in the lab manual 757 00:31:16,910 --> 00:31:19,410 that you will use to calculate the theoretical boiling point 758 00:31:19,410 --> 00:31:21,880 of water at whatever the atmospheric pressure is 759 00:31:21,880 --> 00:31:22,380 on that day. 760 00:31:22,380 --> 00:31:24,090 So you'll go get the barometer from the lab 761 00:31:24,090 --> 00:31:25,410 like we brought down to the river. 762 00:31:25,410 --> 00:31:26,760 You can measure the pressure in lab 763 00:31:26,760 --> 00:31:28,740 because we know that boiling point is related 764 00:31:28,740 --> 00:31:31,170 to the pressure in the atmosphere and the vapor 765 00:31:31,170 --> 00:31:34,420 pressure, so there is a correction factor for that. 766 00:31:34,420 --> 00:31:37,355 And then you will plot your theoretical boiling points 767 00:31:37,355 --> 00:31:39,480 and your theoretical freezing point versus the ones 768 00:31:39,480 --> 00:31:40,855 you actually measure, and that'll 769 00:31:40,855 --> 00:31:43,908 give you a two-point calibration curve for your thermometer 770 00:31:43,908 --> 00:31:46,200 that you're going to use to determine the boiling point 771 00:31:46,200 --> 00:31:47,798 of your ester. 772 00:31:47,798 --> 00:31:50,340 The apparatus that we will use to determine the boiling point 773 00:31:50,340 --> 00:31:52,552 of the ester is like so. 774 00:31:52,552 --> 00:31:53,760 You will have your hot plate. 775 00:31:53,760 --> 00:31:55,680 Then you'll have a sand bath, and then you're 776 00:31:55,680 --> 00:31:57,180 going to use a very small test tube. 777 00:31:57,180 --> 00:31:59,340 And you will put a very tiny amount of your ester 778 00:31:59,340 --> 00:32:01,110 in, maybe a milliliter. 779 00:32:01,110 --> 00:32:03,160 And then you will suspend the thermometer. 780 00:32:03,160 --> 00:32:04,290 We're going to use digital thermometers. 781 00:32:04,290 --> 00:32:06,480 You'll suspend the thermometer a few centimeters 782 00:32:06,480 --> 00:32:09,660 above the surface of your liquid, 783 00:32:09,660 --> 00:32:11,938 and when you heat this up, your liquid will vaporize. 784 00:32:11,938 --> 00:32:13,980 It'll hit the thermometer tip and it'll condense, 785 00:32:13,980 --> 00:32:18,340 so you'll see drips coming off of the tip of your thermometer. 786 00:32:18,340 --> 00:32:22,560 And the temperature will start to go up, and you want to wait. 787 00:32:22,560 --> 00:32:24,982 So the second thing that you'll need is a lot of patience. 788 00:32:24,982 --> 00:32:26,440 So the temperature will go up very, 789 00:32:26,440 --> 00:32:30,082 very slowly as the vapor reaches the boiling point. 790 00:32:30,082 --> 00:32:32,415 So if you've ever boiled water and you cooked something, 791 00:32:32,415 --> 00:32:34,457 you know that you'll start to see steam and water 792 00:32:34,457 --> 00:32:37,140 vapor before the liquid itself is boiling. 793 00:32:37,140 --> 00:32:38,140 Same thing happens here. 794 00:32:38,140 --> 00:32:40,432 You'll start to see the drips, but then the temperature 795 00:32:40,432 --> 00:32:41,440 may still be going up. 796 00:32:41,440 --> 00:32:42,510 So this is one of those things that you 797 00:32:42,510 --> 00:32:44,893 don't want to sit there and watch because you will become 798 00:32:44,893 --> 00:32:46,560 very impatient and you'll say, oh, good, 799 00:32:46,560 --> 00:32:48,435 the temperature hasn't changed in 30 seconds. 800 00:32:48,435 --> 00:32:49,380 This must be it. 801 00:32:49,380 --> 00:32:50,800 But then if you come back in five minutes, 802 00:32:50,800 --> 00:32:51,900 the temperature has indeed gone up, 803 00:32:51,900 --> 00:32:53,890 and then you have the incorrect boiling point. 804 00:32:53,890 --> 00:32:56,140 So this is one of those things you can set up and then 805 00:32:56,140 --> 00:32:57,390 check on it after a while. 806 00:32:57,390 --> 00:32:59,250 And once the temperature stops increasing, 807 00:32:59,250 --> 00:33:00,583 that will be your boiling point. 808 00:33:02,833 --> 00:33:04,250 The next thing that you will do is 809 00:33:04,250 --> 00:33:06,260 you will determine the density of your unknown, 810 00:33:06,260 --> 00:33:10,110 and this is our density instrument that is in the lab. 811 00:33:10,110 --> 00:33:13,580 So instead of having to measure the mass and the volume 812 00:33:13,580 --> 00:33:15,650 yourself to get grams over milliliters, which 813 00:33:15,650 --> 00:33:19,340 is our unit of density, you can inject your sample 814 00:33:19,340 --> 00:33:22,070 into the side of this instrument. 815 00:33:22,070 --> 00:33:24,380 So there's the little lower-lock valve here, 816 00:33:24,380 --> 00:33:27,275 and there's a syringe, so you will inject your sample in 817 00:33:27,275 --> 00:33:29,210 and it'll fill up this tube. 818 00:33:29,210 --> 00:33:31,805 The instrument stays at 20 degrees Celsius 819 00:33:31,805 --> 00:33:34,370 so that we know for sure that it is the density at 20 degrees 820 00:33:34,370 --> 00:33:35,790 Celsius. 821 00:33:35,790 --> 00:33:37,255 And then you will press Go and it 822 00:33:37,255 --> 00:33:38,630 will measure the density for you, 823 00:33:38,630 --> 00:33:42,600 and it'll pop out the density number right there. 824 00:33:42,600 --> 00:33:44,490 So very simple, and then you can use that 825 00:33:44,490 --> 00:33:46,670 as an identifying characteristic of your ester, 826 00:33:46,670 --> 00:33:49,170 and you can compare that again to the chart in the beginning 827 00:33:49,170 --> 00:33:51,960 of the lab manual to use as information to help 828 00:33:51,960 --> 00:33:55,020 you identify your unknown. 829 00:33:55,020 --> 00:33:56,970 Then we're going to measure refractive index. 830 00:33:56,970 --> 00:33:58,920 We talked about refractometry a little bit 831 00:33:58,920 --> 00:34:01,130 in the essential oil lab. 832 00:34:01,130 --> 00:34:03,630 In the essential oil lab, we used it to-- oh, that's a typo. 833 00:34:03,630 --> 00:34:06,120 In the essential oil lab, we used the refractometer 834 00:34:06,120 --> 00:34:10,270 to determine the purity of our samples, but in this lab, 835 00:34:10,270 --> 00:34:12,060 we're going to use it as an identification 836 00:34:12,060 --> 00:34:13,620 technique for our esters. 837 00:34:13,620 --> 00:34:16,290 So every liquid has a characteristic refractive 838 00:34:16,290 --> 00:34:18,773 index, so we can measure the refractive index, compare it 839 00:34:18,773 --> 00:34:20,940 to the literature value, and that will also help you 840 00:34:20,940 --> 00:34:22,980 identify your unknown ester. 841 00:34:26,142 --> 00:34:28,100 The second to last technique we're going to use 842 00:34:28,100 --> 00:34:29,330 is NMR spectroscopy. 843 00:34:29,330 --> 00:34:31,699 And how many of you guys have seen 844 00:34:31,699 --> 00:34:36,480 NMR before in your classes? 845 00:34:36,480 --> 00:34:37,980 A few people. 846 00:34:37,980 --> 00:34:43,050 All right, so in, I think about two weeks, 847 00:34:43,050 --> 00:34:45,815 Walt Massefski, who is the Director of the NMR Facility 848 00:34:45,815 --> 00:34:47,190 here in the chemistry department, 849 00:34:47,190 --> 00:34:52,060 is going to come and do a very, very thorough lecture on NMR 850 00:34:52,060 --> 00:34:55,607 and how it works and how to interpret it. 851 00:34:55,607 --> 00:34:58,190 Unfortunately, that lecture will happen after some of you guys 852 00:34:58,190 --> 00:35:01,670 take these spectra in the actual lab, 853 00:35:01,670 --> 00:35:07,850 so I will do a quick briefing on NMR because we have some time. 854 00:35:07,850 --> 00:35:10,520 And then again, stay tuned. 855 00:35:10,520 --> 00:35:13,640 You will get a much, much better idea of this technique 856 00:35:13,640 --> 00:35:16,910 from Walt in a couple of weeks. 857 00:35:16,910 --> 00:35:19,010 So NMR spectroscopy, the idea behind it 858 00:35:19,010 --> 00:35:21,380 is that it uses a very strong magnetic field 859 00:35:21,380 --> 00:35:23,967 to align nuclear spin states. 860 00:35:23,967 --> 00:35:26,300 And you don't have to know too much about that, at least 861 00:35:26,300 --> 00:35:27,207 for right now. 862 00:35:27,207 --> 00:35:28,790 I'm sure Walt will talk more about it. 863 00:35:28,790 --> 00:35:33,720 But the hydrogen nucleus has a spin associated with it, 864 00:35:33,720 --> 00:35:37,610 and if you apply a magnetic field in a certain direction, 865 00:35:37,610 --> 00:35:40,760 the spin can either align with the magnetic field, which 866 00:35:40,760 --> 00:35:43,492 is the lower energy state, or it can 867 00:35:43,492 --> 00:35:45,950 go against the magnetic field, which is a little bit higher 868 00:35:45,950 --> 00:35:46,450 in energy. 869 00:35:46,450 --> 00:35:48,500 And so this is a difference in energy here. 870 00:35:53,550 --> 00:35:56,180 So once you have your protons in your field-- 871 00:35:56,180 --> 00:35:58,555 and you can do other nuclei too, but we're going to focus 872 00:35:58,555 --> 00:36:00,490 on protons for the moment-- 873 00:36:00,490 --> 00:36:01,990 there's a radio frequency pulse that 874 00:36:01,990 --> 00:36:07,220 is applied that causes some of these spins to flip. 875 00:36:07,220 --> 00:36:10,600 And then you remove the radio frequency pulse, reapply 876 00:36:10,600 --> 00:36:12,190 the magnetic field, and then you wait 877 00:36:12,190 --> 00:36:16,265 for the spin states to go back down to the ground state. 878 00:36:16,265 --> 00:36:18,390 And because there's an energy difference associated 879 00:36:18,390 --> 00:36:19,973 with getting the spin to flip, there's 880 00:36:19,973 --> 00:36:23,430 also an energy difference associated with when it 881 00:36:23,430 --> 00:36:25,150 goes back to its ground state. 882 00:36:25,150 --> 00:36:27,540 So it will emit energy at a certain frequency 883 00:36:27,540 --> 00:36:30,750 depending on the environment of the proton. 884 00:36:30,750 --> 00:36:34,710 We can measure the energy that gets emitted and plotted, 885 00:36:34,710 --> 00:36:38,810 Fourier-transform it, and then you get an NMR spectrum. 886 00:36:38,810 --> 00:36:41,870 This is the really quick, five-minute version. 887 00:36:41,870 --> 00:36:45,150 This will make a lot more sense when Walt talks about it later. 888 00:36:45,150 --> 00:36:46,820 So the important thing to note here 889 00:36:46,820 --> 00:36:50,330 is that the frequency of the energy that a proton emits 890 00:36:50,330 --> 00:36:53,030 as it changes spin state is related to the environment 891 00:36:53,030 --> 00:36:56,310 of the proton. 892 00:36:56,310 --> 00:36:58,490 So we can use this to get information 893 00:36:58,490 --> 00:37:01,070 about the different protons in our molecule, 894 00:37:01,070 --> 00:37:04,190 and we can determine connectivity, 895 00:37:04,190 --> 00:37:05,750 the number of protons that we have, 896 00:37:05,750 --> 00:37:08,000 and some information about how they're bonded together 897 00:37:08,000 --> 00:37:10,430 depending on the different NMR experiments that you do. 898 00:37:10,430 --> 00:37:13,310 And the three major pieces of information 899 00:37:13,310 --> 00:37:17,210 that we will be using in our lab are the chemical shift 900 00:37:17,210 --> 00:37:18,000 of the proton-- 901 00:37:18,000 --> 00:37:20,960 so that's again related to the frequency of the energy-- 902 00:37:20,960 --> 00:37:23,720 the integration-- this tells you how many protons there are-- 903 00:37:23,720 --> 00:37:25,500 and then sometimes the coupling. 904 00:37:25,500 --> 00:37:27,410 So if there are protons next to each other, 905 00:37:27,410 --> 00:37:29,030 they will split each other's signals 906 00:37:29,030 --> 00:37:32,970 and you'll get multiple lines in your NMR spectrum. 907 00:37:32,970 --> 00:37:34,750 So as a really, really quick example, 908 00:37:34,750 --> 00:37:39,870 we can look at our favorite ester here, ethyl acetate, 909 00:37:39,870 --> 00:37:43,620 and we can look at the different types of protons that it has. 910 00:37:43,620 --> 00:37:49,190 So how many types of protons are in this molecule? 911 00:37:49,190 --> 00:37:50,830 Three. 912 00:37:50,830 --> 00:37:55,120 So we have these methyl protons here, the ethyl protons here, 913 00:37:55,120 --> 00:37:58,690 and then these methyl protons over there. 914 00:37:58,690 --> 00:38:01,650 So these three are all in the same chemical environment. 915 00:38:01,650 --> 00:38:03,400 These are in the same chemical environment 916 00:38:03,400 --> 00:38:05,358 and these are in the same chemical environment. 917 00:38:05,358 --> 00:38:08,080 So we should expect to see three signals in the NMR 918 00:38:08,080 --> 00:38:10,620 spectrum of ethyl acetate. 919 00:38:10,620 --> 00:38:14,810 So the way that an NMR spectrum is laid out, 920 00:38:14,810 --> 00:38:21,540 it's on a scale of 0 to 12, give or take. 921 00:38:21,540 --> 00:38:24,090 It can go beyond that, but for the purposes 922 00:38:24,090 --> 00:38:26,550 of most organic molecules, all of the peaks 923 00:38:26,550 --> 00:38:29,480 will be found in this region. 924 00:38:29,480 --> 00:38:32,620 And the location that a peak appears 925 00:38:32,620 --> 00:38:34,480 or a proton peak appears is again 926 00:38:34,480 --> 00:38:36,730 related to its chemical environment. 927 00:38:36,730 --> 00:38:38,590 And the things that are very alkyl 928 00:38:38,590 --> 00:38:40,570 or have a lot of stages around them 929 00:38:40,570 --> 00:38:42,800 are going to be further upfield. 930 00:38:42,800 --> 00:38:48,870 We call this upfield with a lower PPM number. 931 00:38:52,210 --> 00:38:55,840 And things that are closer to oxygens 932 00:38:55,840 --> 00:38:57,550 or electron-withdrawing groups are 933 00:38:57,550 --> 00:38:59,500 going to be-- they call it deshielded. 934 00:38:59,500 --> 00:39:02,540 So the electrons are withdrawn away from those protons. 935 00:39:02,540 --> 00:39:05,810 It doesn't shield= them from the magnetic field as much. 936 00:39:05,810 --> 00:39:12,940 So they come up more downfield, and the way that you 937 00:39:12,940 --> 00:39:18,890 can remember that is downfield or deshielded 938 00:39:18,890 --> 00:39:21,530 both start with D. 939 00:39:21,530 --> 00:39:27,980 And so if we look at these protons, which of these do 940 00:39:27,980 --> 00:39:31,370 we think is going to be the most upfield or the furthest away 941 00:39:31,370 --> 00:39:34,590 from all of our oxygens? 942 00:39:34,590 --> 00:39:36,090 This stuff all the way on the right? 943 00:39:36,090 --> 00:39:37,700 Yeah. 944 00:39:37,700 --> 00:39:42,940 I just want to make sure that I am doing this right. 945 00:39:42,940 --> 00:39:47,840 So yes, these methyl protons will 946 00:39:47,840 --> 00:39:51,317 be the furthest to the right, and you'll get a signal here. 947 00:39:51,317 --> 00:39:53,150 And so this signal, the chemical shift value 948 00:39:53,150 --> 00:39:57,460 will be somewhere probably around 1 or 2. 949 00:39:57,460 --> 00:40:00,220 And then the integration tells you how many protons it's for, 950 00:40:00,220 --> 00:40:01,970 and that shows up down here at the bottom. 951 00:40:01,970 --> 00:40:05,070 So how many protons will the signal equal? 952 00:40:05,070 --> 00:40:07,840 Three from our methyl group. 953 00:40:07,840 --> 00:40:11,460 All right, so if we look at the remaining two 954 00:40:11,460 --> 00:40:15,810 groups, which one do we think would be kind of the middle? 955 00:40:18,600 --> 00:40:20,370 All the way on the left. 956 00:40:20,370 --> 00:40:23,700 So these protons here are right next to an oxygen, so they're 957 00:40:23,700 --> 00:40:26,760 going to be more deshielded, and these have a carbon in between, 958 00:40:26,760 --> 00:40:28,390 so these will be our next signal. 959 00:40:28,390 --> 00:40:30,847 So then we'll have another signal here. 960 00:40:30,847 --> 00:40:31,555 How many protons? 961 00:40:34,400 --> 00:40:35,510 From this group, three. 962 00:40:38,020 --> 00:40:41,950 And so that leaves our methylene group over here. 963 00:40:41,950 --> 00:40:44,260 That will have another signal that's further downfield, 964 00:40:44,260 --> 00:40:48,820 and this one will be two protons. 965 00:40:48,820 --> 00:40:50,440 So already, you can see that there 966 00:40:50,440 --> 00:40:52,540 are different ways that you can use this 967 00:40:52,540 --> 00:40:54,590 to identify your molecules. 968 00:40:54,590 --> 00:40:59,037 So if you count up the number of different unique protons 969 00:40:59,037 --> 00:41:01,620 there are, then you can look at the number of signals you see, 970 00:41:01,620 --> 00:41:04,560 and that is one way to identify your product. 971 00:41:04,560 --> 00:41:07,560 You can also use the coupling, which 972 00:41:07,560 --> 00:41:12,610 is what is going to break these signals into not just one peak, 973 00:41:12,610 --> 00:41:14,090 but it'll be a few. 974 00:41:14,090 --> 00:41:16,300 So coupling happens when there are protons 975 00:41:16,300 --> 00:41:17,960 that are next to each other. 976 00:41:17,960 --> 00:41:23,040 So this methyl group is next to two other protons, right. 977 00:41:23,040 --> 00:41:25,800 And so each of these protons, each of its neighbors, 978 00:41:25,800 --> 00:41:29,470 will split this signal one time. 979 00:41:29,470 --> 00:41:35,150 So if you have your signal and it gets split once, 980 00:41:35,150 --> 00:41:37,500 then you have two signals, and then 981 00:41:37,500 --> 00:41:40,790 if it gets split again in an equal magnitude, 982 00:41:40,790 --> 00:41:43,320 you end up with three signals. 983 00:41:43,320 --> 00:41:47,680 So this splitting kind of combines and this peak 984 00:41:47,680 --> 00:41:49,430 gets a little bit bigger. 985 00:41:49,430 --> 00:41:51,110 So this is what is called a triplet. 986 00:41:51,110 --> 00:41:59,060 So if you have two neighbors, you get a triplet. 987 00:41:59,060 --> 00:42:03,240 So this peak, that methyl group will actually 988 00:42:03,240 --> 00:42:06,960 look something like this. 989 00:42:06,960 --> 00:42:09,210 It'll have three peaks to it with the middle one 990 00:42:09,210 --> 00:42:11,543 being the biggest, and that's the characteristic pattern 991 00:42:11,543 --> 00:42:14,130 of a triplet. 992 00:42:14,130 --> 00:42:17,390 What about our ethyl group here, or ethylene group, 993 00:42:17,390 --> 00:42:18,390 methylene group? 994 00:42:18,390 --> 00:42:20,690 We have our two protons. 995 00:42:20,690 --> 00:42:25,910 How many neighbors does this group have, proton neighbors? 996 00:42:25,910 --> 00:42:30,790 So this has three neighbors. 997 00:42:30,790 --> 00:42:33,790 So that signal is going to get split three times. 998 00:42:33,790 --> 00:42:34,870 So you'll split it once. 999 00:42:39,120 --> 00:42:42,420 Split it again, so that would be our triplet. 1000 00:42:42,420 --> 00:42:50,940 And then if we split it a third time, we get four lines. 1001 00:42:50,940 --> 00:42:53,820 So this proton signal will actually 1002 00:42:53,820 --> 00:42:56,470 look something like that. 1003 00:43:00,930 --> 00:43:03,610 How many proton neighbors does this have? 1004 00:43:03,610 --> 00:43:04,960 None, so will this get split? 1005 00:43:07,500 --> 00:43:08,640 No. 1006 00:43:08,640 --> 00:43:11,070 So this will stay as a singlet, one single peak, 1007 00:43:11,070 --> 00:43:13,215 because it does not have any proton neighbors. 1008 00:43:16,935 --> 00:43:19,600 So anyone have any questions about where all of this 1009 00:43:19,600 --> 00:43:20,100 came from? 1010 00:43:26,620 --> 00:43:32,072 So again, that was the super quick version of NMR 1011 00:43:32,072 --> 00:43:34,280 and the type of information that you can get from it. 1012 00:43:34,280 --> 00:43:36,170 So when you are looking at the structures 1013 00:43:36,170 --> 00:43:38,765 of the potential esters that you think you may have, 1014 00:43:38,765 --> 00:43:40,670 you can probably narrow it down based 1015 00:43:40,670 --> 00:43:44,230 on your boiling point in your refractive index, your density. 1016 00:43:44,230 --> 00:43:45,730 And you can narrow it down to a few, 1017 00:43:45,730 --> 00:43:47,480 and then you will draw out the structures. 1018 00:43:47,480 --> 00:43:49,420 And then you can, based on the structure, 1019 00:43:49,420 --> 00:43:52,480 predict how many NMR signals you expect to see. 1020 00:43:52,480 --> 00:43:56,537 And you can figure out what you expect the splitting to be, 1021 00:43:56,537 --> 00:43:58,370 so if you expect them to all be single peaks 1022 00:43:58,370 --> 00:44:02,580 or if you expect to see different types of multiplets. 1023 00:44:02,580 --> 00:44:04,620 And then when you get your NMR spectrum, 1024 00:44:04,620 --> 00:44:06,702 you can compare the number of peaks, 1025 00:44:06,702 --> 00:44:07,910 the integration of the peaks. 1026 00:44:07,910 --> 00:44:09,510 So if you know that you have a methyl group, 1027 00:44:09,510 --> 00:44:12,060 you should be looking for some signals that integrate to 3. 1028 00:44:14,730 --> 00:44:18,960 And that is how you can use this as a technique to identify 1029 00:44:18,960 --> 00:44:21,000 the structure of your unknown. 1030 00:44:23,610 --> 00:44:25,800 And again, Walt will do a much better job explaining 1031 00:44:25,800 --> 00:44:27,487 all of this in a bit. 1032 00:44:27,487 --> 00:44:29,070 But just so you've seen it, before you 1033 00:44:29,070 --> 00:44:31,860 get a chance to take your spectrum in lab, 1034 00:44:31,860 --> 00:44:36,720 that is a quick introduction. 1035 00:44:36,720 --> 00:44:38,615 So once you have all of this information, 1036 00:44:38,615 --> 00:44:40,740 you have your boiling point, your refractive index, 1037 00:44:40,740 --> 00:44:43,860 your density, your NMR spectrum, your IR spectrum, 1038 00:44:43,860 --> 00:44:45,990 you're going to attempt to identify your unknown, 1039 00:44:45,990 --> 00:44:47,460 and this should all happen at the end of day three. 1040 00:44:47,460 --> 00:44:48,630 You'll have all of this information, 1041 00:44:48,630 --> 00:44:49,950 and then you'll be overwhelmed. 1042 00:44:49,950 --> 00:44:51,750 You'll sit down, put it all together 1043 00:44:51,750 --> 00:44:54,690 and try to figure out which of those unknowns in that table 1044 00:44:54,690 --> 00:44:56,427 is the one that you made. 1045 00:44:56,427 --> 00:44:58,010 You'll fill out an identification form 1046 00:44:58,010 --> 00:44:59,720 that your TAs will give you, and then 1047 00:44:59,720 --> 00:45:01,887 you will bring it to your TA at the beginning of day 1048 00:45:01,887 --> 00:45:04,550 four on the lab and you will say, this is my ester. 1049 00:45:04,550 --> 00:45:07,070 And they will tell you if you are right or wrong, 1050 00:45:07,070 --> 00:45:10,060 and you'll find out that day if you were correct or not. 1051 00:45:10,060 --> 00:45:11,843 And then you will do one more technique 1052 00:45:11,843 --> 00:45:13,010 for your final confirmation. 1053 00:45:13,010 --> 00:45:15,710 So if you already know, then your mass spectrum 1054 00:45:15,710 --> 00:45:18,090 should be super confirmation for you. 1055 00:45:18,090 --> 00:45:19,850 And if you were a little bit off, then 1056 00:45:19,850 --> 00:45:21,225 hopefully your mass spectrum will 1057 00:45:21,225 --> 00:45:22,910 be that last piece that helps you to get 1058 00:45:22,910 --> 00:45:26,880 your final identification. 1059 00:45:26,880 --> 00:45:29,130 Mass spectrometry, you have already seen a little bit. 1060 00:45:29,130 --> 00:45:32,365 We did the ICPMS in our last lab. 1061 00:45:32,365 --> 00:45:34,240 But there are different, many different types 1062 00:45:34,240 --> 00:45:36,130 of mass spectrometry, and a bunch of different ways 1063 00:45:36,130 --> 00:45:37,550 that you can use that technique. 1064 00:45:37,550 --> 00:45:39,820 So ICP uses plasma to break the compounds apart 1065 00:45:39,820 --> 00:45:42,340 into their atoms and ionizes the compounds that way, 1066 00:45:42,340 --> 00:45:44,308 if you remember, hopefully. 1067 00:45:44,308 --> 00:45:45,850 What we're going to be doing this lab 1068 00:45:45,850 --> 00:45:48,320 is electronic impact mass spectrometry, 1069 00:45:48,320 --> 00:45:50,410 which instead of using plasma just 1070 00:45:50,410 --> 00:45:54,550 shoots a high-energy beam of electrons at your molecule. 1071 00:45:54,550 --> 00:45:56,080 And it doesn't have enough energy 1072 00:45:56,080 --> 00:45:58,930 to break your molecule apart into its atoms or anything, 1073 00:45:58,930 --> 00:46:01,030 but what's going to happen is the electrons 1074 00:46:01,030 --> 00:46:03,880 will hit the compound and it will eject an electron 1075 00:46:03,880 --> 00:46:05,060 from the compound. 1076 00:46:05,060 --> 00:46:07,595 So you'll make what is called a radical cation. 1077 00:46:07,595 --> 00:46:10,220 So it'll have one less electron, so it'll be a positive charge, 1078 00:46:10,220 --> 00:46:13,720 but it only lost one electron, and since it's organic-y, 1079 00:46:13,720 --> 00:46:16,480 it will be a radical. 1080 00:46:16,480 --> 00:46:18,640 This also frequently causes the molecule 1081 00:46:18,640 --> 00:46:20,290 to break apart, not always. 1082 00:46:20,290 --> 00:46:22,853 Sometimes you will get the radical cation 1083 00:46:22,853 --> 00:46:24,520 of your whole molecule that will make it 1084 00:46:24,520 --> 00:46:25,937 through the mass detector, and you 1085 00:46:25,937 --> 00:46:29,950 will get the mass of your actual compound. 1086 00:46:29,950 --> 00:46:31,450 And other times, it'll break apart 1087 00:46:31,450 --> 00:46:34,000 and you will see a bunch of pieces of your compounds. 1088 00:46:34,000 --> 00:46:37,910 You'll see the mass of different fragments of your molecule. 1089 00:46:37,910 --> 00:46:42,960 So you can use either the mass of your molecular ion-- 1090 00:46:42,960 --> 00:46:46,120 so I'll show you what this looks like in a second. 1091 00:46:46,120 --> 00:46:49,330 So this is what the instrument looks like. 1092 00:46:49,330 --> 00:46:51,070 It's right near the ICPMS. 1093 00:46:51,070 --> 00:46:54,940 You may or may not have seen it, and it is slightly older 1094 00:46:54,940 --> 00:46:58,218 and looks a lot like the GC that we talked about before 1095 00:46:58,218 --> 00:46:59,260 in the essential oil lab. 1096 00:46:59,260 --> 00:47:00,760 And that is because this is actually 1097 00:47:00,760 --> 00:47:02,750 a GC mass spectrometer. 1098 00:47:02,750 --> 00:47:03,977 So you inject your compound. 1099 00:47:03,977 --> 00:47:05,810 It actually goes through gas chromatography, 1100 00:47:05,810 --> 00:47:06,880 so if you have more than one compound, 1101 00:47:06,880 --> 00:47:08,962 it'll split it into the different compounds. 1102 00:47:08,962 --> 00:47:10,420 And then it'll take a mass spectrum 1103 00:47:10,420 --> 00:47:12,250 of each of those compounds. 1104 00:47:12,250 --> 00:47:15,493 We hopefully are only going to be injecting one compound in, 1105 00:47:15,493 --> 00:47:17,410 so you hopefully purified it sufficiently well 1106 00:47:17,410 --> 00:47:18,190 at this point. 1107 00:47:18,190 --> 00:47:20,065 But then it'll still give us a mass spectrum, 1108 00:47:20,065 --> 00:47:22,370 and the mass spectrum looks like this. 1109 00:47:22,370 --> 00:47:26,807 So this is our mass-to-charge ratio or our mass units. 1110 00:47:26,807 --> 00:47:29,140 So usually, the furthest thing, the heaviest thing, that 1111 00:47:29,140 --> 00:47:30,340 is where you will look to see if that 1112 00:47:30,340 --> 00:47:31,990 matches with the expected molecular weight 1113 00:47:31,990 --> 00:47:32,560 of your compound. 1114 00:47:32,560 --> 00:47:33,610 That's your molecular ion. 1115 00:47:33,610 --> 00:47:35,110 So if it gets hit with the electron, 1116 00:47:35,110 --> 00:47:37,815 forms a radical cation and doesn't break apart anymore, 1117 00:47:37,815 --> 00:47:39,690 you will see a peak at your molecular weight. 1118 00:47:39,690 --> 00:47:44,198 And so that is a giveaway of yes, this is my molecule. 1119 00:47:44,198 --> 00:47:45,490 Sometimes, that doesn't happen. 1120 00:47:45,490 --> 00:47:47,532 If it's really unstable, it'll break into pieces, 1121 00:47:47,532 --> 00:47:50,230 and you will see-- so each of these 1122 00:47:50,230 --> 00:47:54,430 represents a piece of the molecule that has broken off. 1123 00:47:54,430 --> 00:47:57,340 So frequently, you'll see losses of 15. 1124 00:47:57,340 --> 00:47:59,110 So that's when a methyl group breaks off. 1125 00:47:59,110 --> 00:48:01,990 And Dr. Dolan will be talking a lot more 1126 00:48:01,990 --> 00:48:03,657 about mass spectrometry and what you 1127 00:48:03,657 --> 00:48:05,740 will do with this information and how it all works 1128 00:48:05,740 --> 00:48:08,350 in another lecture coming up. 1129 00:48:08,350 --> 00:48:10,270 Just to give you, again, an idea before you 1130 00:48:10,270 --> 00:48:12,130 see it and have to do it in the lab. 1131 00:48:12,130 --> 00:48:13,180 This is just a quick overview and you'll 1132 00:48:13,180 --> 00:48:15,013 get a lot more detail about what all of this 1133 00:48:15,013 --> 00:48:18,420 means coming up in a couple of lectures. 1134 00:48:18,420 --> 00:48:22,320 Last but not least, safety for this lab is very important. 1135 00:48:22,320 --> 00:48:24,900 The carboxylic acids are corrosive and toxic. 1136 00:48:24,900 --> 00:48:26,730 They smell terrible. 1137 00:48:26,730 --> 00:48:27,660 You can ask Tristan. 1138 00:48:27,660 --> 00:48:31,520 He was the one who made all of the unknowns. 1139 00:48:31,520 --> 00:48:35,370 And Brydon did the alcohols, so he got it slightly better, 1140 00:48:35,370 --> 00:48:39,210 but Tristan will tell you that the carboxylic acids are 1141 00:48:39,210 --> 00:48:41,280 very nasty to work with. 1142 00:48:41,280 --> 00:48:43,647 Sulfuric acid is also highly corrosive, 1143 00:48:43,647 --> 00:48:45,480 so you don't want to get that on your hands. 1144 00:48:45,480 --> 00:48:46,620 And then you want to vent the sep funnel, 1145 00:48:46,620 --> 00:48:47,890 like we said, away from people. 1146 00:48:47,890 --> 00:48:49,080 So if you're working in a hood with someone, 1147 00:48:49,080 --> 00:48:50,040 make sure that they're not around. 1148 00:48:50,040 --> 00:48:51,582 Don't turn around to talk to somebody 1149 00:48:51,582 --> 00:48:54,087 and point it in their face. 1150 00:48:54,087 --> 00:48:55,670 The starting materials smell very bad. 1151 00:48:55,670 --> 00:48:57,170 Your product will smell really nice, 1152 00:48:57,170 --> 00:49:00,720 but it'll still smell a lot, so keep everything in the hood. 1153 00:49:00,720 --> 00:49:02,480 This is a very, very smelly lab. 1154 00:49:02,480 --> 00:49:04,370 Even if you keep everything in the hood, if you're walking by, 1155 00:49:04,370 --> 00:49:06,500 which everybody is doing this, you will know. 1156 00:49:06,500 --> 00:49:08,770 So we want to limit the amount of fumes 1157 00:49:08,770 --> 00:49:09,770 that get out in the lab. 1158 00:49:09,770 --> 00:49:11,240 Keep everything in the hood. 1159 00:49:11,240 --> 00:49:12,920 Do not put vials in the glass waste. 1160 00:49:12,920 --> 00:49:16,000 If anything breaks, or if you like break a pipette 1161 00:49:16,000 --> 00:49:17,750 or if you break a beaker or something that 1162 00:49:17,750 --> 00:49:21,145 has contacted your solutions from the ester lab, 1163 00:49:21,145 --> 00:49:23,270 there will be a separate waste container for those. 1164 00:49:23,270 --> 00:49:25,952 Your TAs will come around with a capped, plastic solid-waste 1165 00:49:25,952 --> 00:49:27,410 container to collect all your vials 1166 00:49:27,410 --> 00:49:29,690 so that they are not in the glass waste 1167 00:49:29,690 --> 00:49:32,910 stinking up the entire lab. 1168 00:49:32,910 --> 00:49:34,230 And this is key for everybody. 1169 00:49:34,230 --> 00:49:35,430 Regardless of what lab you're doing-- 1170 00:49:35,430 --> 00:49:36,550 so starting on Wednesday and Thursday, 1171 00:49:36,550 --> 00:49:38,383 we're going to be doing three different labs 1172 00:49:38,383 --> 00:49:40,800 at the same time, and we're going to try to keep the waste 1173 00:49:40,800 --> 00:49:44,160 containers in the bays with the proper labs 1174 00:49:44,160 --> 00:49:45,390 they're associated with. 1175 00:49:45,390 --> 00:49:48,510 But pay attention to the waste labels. 1176 00:49:48,510 --> 00:49:49,530 Read the red tag. 1177 00:49:49,530 --> 00:49:50,430 If you're holding something and you're 1178 00:49:50,430 --> 00:49:52,218 going to put it in the waste container, 1179 00:49:52,218 --> 00:49:53,760 take the extra second to make sure it 1180 00:49:53,760 --> 00:49:56,130 is the right one for the lab that you are doing. 1181 00:49:56,130 --> 00:49:58,710 There will be three different sets of waste containers 1182 00:49:58,710 --> 00:50:02,820 out there, and we do not want to mix in between, especially not 1183 00:50:02,820 --> 00:50:05,190 acetone with the catalase waste. 1184 00:50:05,190 --> 00:50:07,400 If you remember from before-- 1185 00:50:07,400 --> 00:50:08,650 we may have talked about this. 1186 00:50:08,650 --> 00:50:09,858 You will hear about it again. 1187 00:50:09,858 --> 00:50:13,980 If you mix the acetone from any of these organic-y labs 1188 00:50:13,980 --> 00:50:16,140 with the hydrogen peroxide from the catalse waste, 1189 00:50:16,140 --> 00:50:18,840 you will generate explosives. 1190 00:50:18,840 --> 00:50:20,840 So we are not going to do that because everybody 1191 00:50:20,840 --> 00:50:23,300 is going to read the labels and dispose of their waste 1192 00:50:23,300 --> 00:50:25,460 properly in this lab, and keep everything 1193 00:50:25,460 --> 00:50:28,090 in the hood that should be. 1194 00:50:28,090 --> 00:50:28,930 Good? 1195 00:50:28,930 --> 00:50:30,780 Excellent.