1 00:00:00,000 --> 00:00:02,840 PHIL: The prize for the biggest crystal is a lunch 2 00:00:02,840 --> 00:00:07,900 with John and the TAs at Legal Seafood, which I'm personally 3 00:00:07,900 --> 00:00:10,016 very excited about. 4 00:00:10,016 --> 00:00:40,520 [MUSIC PLAYING] 5 00:00:40,520 --> 00:00:43,490 NARRATOR: Today the students are going to learn a totally 6 00:00:43,490 --> 00:00:46,165 different technique, recrystallization. 7 00:00:46,165 --> 00:00:49,120 PHIL: Pesticides, pharmaceuticals, food 8 00:00:49,120 --> 00:00:52,870 colorings, and products where they have to produce tons per 9 00:00:52,870 --> 00:00:56,510 year, recrystallization is the key method. 10 00:00:56,510 --> 00:00:58,550 Yesterday you were working with about 100 11 00:00:58,550 --> 00:00:59,890 megs of each compound. 12 00:00:59,890 --> 00:01:01,975 Today, you're going to be working with 2 grams. 13 00:01:01,975 --> 00:01:04,080 NARRATOR: But there's more on the line than just getting 14 00:01:04,080 --> 00:01:05,800 those 2 grams back. 15 00:01:05,800 --> 00:01:08,750 This is practice for next week's crystal competition. 16 00:01:08,750 --> 00:01:11,010 If the students do well, they'll have a better shot at 17 00:01:11,010 --> 00:01:14,200 winning a free lunch with the teaching staff. 18 00:01:14,200 --> 00:01:16,570 The first step in a recrystallization is to choose 19 00:01:16,570 --> 00:01:18,020 the right solvent. 20 00:01:18,020 --> 00:01:20,520 The students need a liquid that will not dissolve the 21 00:01:20,520 --> 00:01:23,520 target molecule when it's cold, but will dissolve it 22 00:01:23,520 --> 00:01:24,510 when it's hot. 23 00:01:24,510 --> 00:01:27,360 The students then dissolve the sample in hot solvent and 24 00:01:27,360 --> 00:01:29,570 filter out any solid impurities. 25 00:01:29,570 --> 00:01:32,220 Then they cool it down in an ice bath. 26 00:01:32,220 --> 00:01:35,280 The target molecule should crystallized out of solution 27 00:01:35,280 --> 00:01:36,880 forming a pure solid. 28 00:01:36,880 --> 00:01:39,120 The impurities should stay in the liquid. 29 00:01:39,120 --> 00:01:39,560 ANTHONY: Fresh. 30 00:01:39,560 --> 00:01:40,000 IKE: Yep. 31 00:01:40,000 --> 00:01:41,880 That's how we want it. 32 00:01:41,880 --> 00:01:42,690 Crystal clear. 33 00:01:42,690 --> 00:01:45,520 NARRATOR: Ike, Ethan, and Anthony are having 34 00:01:45,520 --> 00:01:47,270 no problems at all. 35 00:01:47,270 --> 00:01:49,840 ETHAN: Ain't nothing too hard for an MIT chemist. 36 00:01:49,840 --> 00:01:53,675 NARRATOR: Hansol, Jason, and Fred on the other hand-- 37 00:01:53,675 --> 00:01:56,815 HANSOL: I made like two, actually three mistakes today. 38 00:01:56,815 --> 00:01:58,870 JASON: I've made so many stupid mistakes today. 39 00:01:58,870 --> 00:02:01,090 HANSOL: Yeah, I didn't realize it would heat that fast. 40 00:02:01,090 --> 00:02:04,250 FRED: Um, it exploded all over the side of my flask. 41 00:02:04,250 --> 00:02:06,170 HANSOL: And then it exploded, so then I had to start over. 42 00:02:06,170 --> 00:02:08,900 PAUL: It started sputtering out and actually 43 00:02:08,900 --> 00:02:09,530 it was kind of scary. 44 00:02:09,530 --> 00:02:12,190 Some of it almost like hit me in the face. 45 00:02:12,190 --> 00:02:13,530 JASON: I've broken a test tube. 46 00:02:13,530 --> 00:02:15,975 HANSOL: And then I put it through a small funnel which 47 00:02:15,975 --> 00:02:16,590 was a total mistake. 48 00:02:16,590 --> 00:02:20,510 JASON: I put too much solvent losing some product. 49 00:02:20,510 --> 00:02:22,595 HANSOL: The funnel, I just dropped it. 50 00:02:22,595 --> 00:02:22,860 So-- 51 00:02:22,860 --> 00:02:26,340 JASON: The yield on this is almost nothing. 52 00:02:26,340 --> 00:02:29,470 NARRATOR: After filtering, washing and drying, everyone 53 00:02:29,470 --> 00:02:32,520 eventually makes it to the final step, weighing the 54 00:02:32,520 --> 00:02:34,770 purified crystals. 55 00:02:34,770 --> 00:02:37,730 Getting 90% yield is the goal. 56 00:02:37,730 --> 00:02:41,180 That would be 1.8 grams of the original crystal. 57 00:02:41,180 --> 00:02:42,570 LEALIA: So far my yield says 1.9 grams. 58 00:02:42,570 --> 00:02:45,270 So I don't know if that's right because there is only 59 00:02:45,270 --> 00:02:46,475 supposed to be two grams. 60 00:02:46,475 --> 00:02:48,640 JULIE: That's probably not going to be that good because 61 00:02:48,640 --> 00:02:50,080 that all I have. 62 00:02:50,080 --> 00:02:53,050 There were some problems with filtering and then also 63 00:02:53,050 --> 00:02:55,630 noticed trying to put the stuff in the beginning, I 64 00:02:55,630 --> 00:02:59,100 spilled it everywhere. 65 00:02:59,100 --> 00:03:01,130 YI-SHIUAN: Is it really pure? 66 00:03:01,130 --> 00:03:03,810 JULIE: 7%. 67 00:03:03,810 --> 00:03:05,160 LEALIA: 101% yield. 68 00:03:05,160 --> 00:03:06,410 JULIE: Good job. 69 00:03:06,410 --> 00:03:08,920 70 00:03:08,920 --> 00:03:10,170 JASON: 3%. 71 00:03:10,170 --> 00:03:11,980 72 00:03:11,980 --> 00:03:14,750 So besides 3% yield, my melting 73 00:03:14,750 --> 00:03:16,000 point's almost perfect. 74 00:03:16,000 --> 00:03:18,334 75 00:03:18,334 --> 00:03:20,990 NARRATOR: For some today, a good start. 76 00:03:20,990 --> 00:03:22,540 For others-- 77 00:03:22,540 --> 00:03:24,560 JASON: 3% yield. 78 00:03:24,560 --> 00:03:25,220 You needed 90%. 79 00:03:25,220 --> 00:03:26,955 I only got 3%. 80 00:03:26,955 --> 00:03:30,530 NARRATOR: Not looking so hot for next week. 81 00:03:30,530 --> 00:03:32,490 Tune in, and see how it all unfolds. 82 00:03:32,490 --> 00:03:37,780 83 00:03:37,780 --> 00:03:40,700 PHIL: Just make observations, write down what could have 84 00:03:40,700 --> 00:03:43,072 went wrong, what you could do differently next time. 85 00:03:43,072 --> 00:03:44,085 JASON: Not spill. 86 00:03:44,085 --> 00:03:50,290 Sleep more beforehand so I don't make mistakes. 87 00:03:50,290 --> 00:03:50,890 Not spill. 88 00:03:50,890 --> 00:03:53,290 PHIL: Take your vitamins. 89 00:03:53,290 --> 00:03:54,790 JASON: Not be an idiot. 90 00:03:54,790 --> 00:03:56,590 I don't know. 91 00:03:56,590 --> 00:04:02,923 [MUSIC PLAYING]