Nitration of Bromobenzene — Transcript

Full transcript

1. 0:00today we're going to do the the two
2. 0:02nitrations of bromobenzene both in the
3. 0:04ortho and para position
4. 0:06there's a couple of things we're going
5. 0:07to pre-weigh right now and then we'll
6. 0:08move over to the apparatus
7. 0:10the one thing about the bromobenzene is
8. 0:12it's a rather sick
9. 0:14third surface type solvent and if you
10. 0:18measure just two milliliters then try to
11. 0:20pour it in you never actually know how
12. 0:22much goes into your
13. 0:23round bottom flask so we want higher
14. 0:26precision then
15. 0:27what we're going to do is measure
16. 0:29actually how much goes into the round
17. 0:31bottom
18. 0:31so we're going to put approximately two
19. 0:33milliliters into here
20. 0:37that's not quite two we might go just a
21. 0:39tiny bit over but
22. 0:41we might just stay a little bit under
23. 0:43having contrast issues
24. 0:46okay we're at about two milliliters
25. 0:48right there
26. 0:49okay there we see so now we're going to
27. 0:52weigh this again
28. 0:54there it goes all right
29. 0:58all right now what we will see when we
30. 1:01add this when we wait a third time
31. 1:03is that not all of the liquid will
32. 1:05actually make it into our round bottom
33. 1:07flask
34. 1:08so while we're here
35. 1:11let's weigh the final product container
36. 1:13we're gonna
37. 1:14put our final product on this watch
38. 1:16glass this is
39. 1:18um how we're gonna measure our yield at
40. 1:20the end
41. 1:21so i'm gonna weigh it
42. 1:27and then we're going to move this one
43. 1:29okay
44. 1:32all right write it down okay so this is
45. 1:35for the end of the experiment
46. 1:37our final product will end up on this
47. 1:39watch glass
48. 1:40okay
49. 1:43now let's move over to this side and
50. 1:46we're going to switch cameras
51. 1:49what we have to do first is add some
52. 1:52sulfuric acid
53. 1:53choose some nitric acid in our round
54. 1:55bottom setup
55. 1:57i have pre-made the setup i'll go
56. 1:59through greasing the joints and it's
57. 2:00okay
58. 2:00we're at this set up i brought the
59. 2:02bromobenzene over we're going to
60. 2:04actually add him
61. 2:05last so i'm going to set him to the side
62. 2:07up front
63. 2:09we have our apparatus that we're going
64. 2:11to do the reflux in
65. 2:12i haven't greasy the joints i'll show
66. 2:14you that in a second
67. 2:16what i want to do is mix the two key
68. 2:19reagents the concentrated nitric acid
69. 2:22and the concentrated sulfuric acid
70. 2:24together
71. 2:26if you've watched the video on
72. 2:29what sulfuric acid does to sugar
73. 2:32it's going to do the exact same thing to
74. 2:34the nitric acid
75. 2:36and because the reaction of dehydrating
76. 2:39is still exothermic
77. 2:41we have to start by adding the two
78. 2:43reagents together in the ice bath
79. 2:46so i have the ice bath now here we're
80. 2:49gonna first
81. 2:51i have six milliliters of concentrated
82. 2:55nitric
83. 2:55acid i'll show you the bottle it came
84. 2:57from
85. 2:59you see that okay
86. 3:02we're gonna pour that in and let it cool
87. 3:05off first
88. 3:13[Music]
89. 3:15and you're not going to be able to see
90. 3:18much through
91. 3:18the double glass of the ice bath but
92. 3:21there's a little pool of nitric acid in
93. 3:23the bottom of the
94. 3:24round bottom flask okay now
95. 3:29we have the concentrated sulfuric acid
96. 3:32that's this game we poured out about 15
97. 3:35milliliters
98. 3:36we're supposed to slowly add it so it
99. 3:39doesn't get
100. 3:41doesn't become carried away
101. 3:45and so it suggests added drop wise
102. 3:50we're going to try that and we're going
103. 3:51to watch to see if
104. 3:54anything takes off inside seems to be
105. 3:57holding pretty steady
106. 4:02and as long as it stays cold
107. 4:05we should be able to stop the reaction
108. 4:07from taking off until we want it to
109. 4:13so i'm kind of swirling the
110. 4:17sulfuric acid around
111. 4:20i'm going to do a gentle swirl
112. 4:23the liquids very good
113. 4:26i've added about five milliliters so far
114. 4:37okay just stay nice and cold there
115. 4:53sadly i'm wearing gloves today professor
116. 4:56ormond made me
117. 4:59first he's worried because both of these
118. 5:02reagents
119. 5:04will instantly react with your skin it's
120. 5:06really cool what they will do to you
121. 5:09which is still good uh it burns it
122. 5:12itches
123. 5:13it sometimes does bubbling and
124. 5:15blistering
125. 5:16there's a lot of cool things that these
126. 5:18guys can do
127. 5:19what's also interesting is this is a lab
128. 5:22that spilled all over my clothes one day
129. 5:26and completely dissolved my shoes away
130. 5:32we had a student at the north vegas lab
131. 5:34get concentrated nitric all over a shirt
132. 5:36and
133. 5:37the safety people came and made him take
134. 5:39a shirt off in the back room
135. 5:40and wash off under the shower it was
136. 5:42pretty scary
137. 5:45we had a grad colleague in my lab at
138. 5:48grad school
139. 5:49get completely covered in concentrated
140. 5:51boiling hot sulfuric acid
141. 5:54the blisters we threw that person
142. 5:56immediately underneath the shower
143. 5:59and they still had blisters all over
144. 6:01their skin
145. 6:02especially on their face so again
146. 6:07these guys react way faster when they're
147. 6:10hot
148. 6:11than when they're cold please refer to
149. 6:13the sugar
150. 6:16experiment with sulfuric acid and you'll
151. 6:18see just how exothermic this can
152. 6:20become
153. 6:23and so that's why we're extra careful
154. 6:26today
155. 6:28we're almost done adding the sulfuric
156. 6:30acid
157. 6:33do we get any color change when you mix
158. 6:35them you shouldn't
159. 6:38if you do you've added them a little too
160. 6:42fast and they became a little bit warm
161. 6:46it all depends on temperature
162. 6:50okay the final squirts
163. 6:55of sulfuric acid we're just about there
164. 7:03so in this reaction the sulfuric acid
165. 7:06actually has two roles to play one is
166. 7:09obviously he's the proton donor to
167. 7:11activate the nitric
168. 7:13acid but another cool property is he's
169. 7:16also a desiccator
170. 7:17which is he sucks the water out of the
171. 7:21system which is literally what he does
172. 7:23in that sugar demo
173. 7:26she sucks the water right out of the
174. 7:28sugar okay
175. 7:30we have carefully added the two chemical
176. 7:33reagents
177. 7:34we're now going to add the bromobenzene
178. 7:38that we weighed earlier
179. 7:40as i said before some of it's going to
180. 7:42be stuck on the on the graduate cylinder
181. 7:45and on the dropper that's why we weighed
182. 7:46them all together
183. 7:48we're going to take one more weight to
184. 7:50see how much
185. 7:51of our starting material actually enters
186. 7:54into this round bottom
187. 7:58so we're gonna very carefully drop this
188. 8:01one in
189. 8:04and it's going well i don't see any
190. 8:06color changes
191. 8:08this is all good
192. 8:17okay so
193. 8:21okay we've added as much bromobenzene as
194. 8:25we can
195. 8:26okay here's the graduate cylinder that
196. 8:28had the bromobenzene in
197. 8:30we added what we could we're now going
198. 8:32to weigh this
199. 8:34and whatever the difference is between
200. 8:36the full and this
201. 8:38will be the massive bromobenzene that
202. 8:40actually went in the flask
203. 8:42it'll be the mass of bromobenzene you
204. 8:44need in your calculations
205. 8:45for your theoretical yield there you go
206. 8:48okay
207. 8:48now that we've weighed our bromobenzene
208. 8:51and we know exactly how much is in there
209. 8:53we are going to grease all our joints
210. 8:56this is our first
211. 8:57lab greasing this semester i just want
212. 8:59to make a comment on the proper way to
213. 9:01grease
214. 9:02and what you do is you use a minimum
215. 9:05amount of grease
216. 9:07and then when you put it in you spin it
217. 9:09so i'm going to demonstrate
218. 9:11first with the stopper
219. 9:14that goes on the top tiny amount of
220. 9:17grease
221. 9:18just a little bit can you guys all see
222. 9:19that i don't know if the contrast helps
223. 9:22or not
224. 9:23when you put it into the stopper
225. 9:27when you spin it around it should make a
226. 9:30clear circle all the way around which
227. 9:32means we have
228. 9:33an airtight seal and we need airtight
229. 9:36seals today
230. 9:37or your solvent will go around so i'm
231. 9:39going to do the same with this joint
232. 9:41and spin it all the way around
233. 9:44make it a nice airtight seal so airtight
234. 9:48seal here
235. 9:49airtight so here we are now setting up
236. 9:53a reflux condenser you guys should know
237. 9:56that water always goes in the bottom and
238. 9:58out the top
239. 9:59another joint needs a tiny bit of grease
240. 10:06grease just the top with just a tiny
241. 10:08amount
242. 10:09that's plenty and then the same thing
243. 10:13spin it around now because the pipes are
244. 10:15in the way i'll just go back and forth
245. 10:17several times
246. 10:22and i should have a nice clear joint
247. 10:24there too
248. 10:26okay the last piece we're going to
249. 10:28grease
250. 10:29is actually this adapter we've hooked it
251. 10:32up to a hose
252. 10:34that goes over to this funnel and in the
253. 10:37solution we're going to put in some
254. 10:39sodium hydroxide
255. 10:41what will happen during this reaction is
256. 10:43the brown gas
257. 10:45uh nitrogen dioxide will come off and we
258. 10:47want to quench it over in that beaker
259. 10:50so one more greasing joint
260. 10:53this will be our last one just a tiny
261. 10:55bit of grease again
262. 10:56everybody see how i just put a tiny
263. 10:58mound on there
264. 11:00we're going to spin it around
265. 11:03back and forth until it's clear all the
266. 11:06way around
267. 11:07the entire joint
268. 11:10okay i have created airtight
269. 11:19i've created airtight grease joints
270. 11:22but i want one i'm going to add a
271. 11:24special clamp right here to make sure
272. 11:26this part doesn't come apart
273. 11:28okay the next step is to turn the water
274. 11:31on
275. 11:32so watch here i'm going to slowly add
276. 11:34water we need it to run continuously
277. 11:37cold water from the tap
278. 11:39so it's running through
279. 11:43i'm going to show you this from behind
280. 11:45we're draining that's a pretty good
281. 11:46rate we're going to keep that going down
282. 11:48the drain
283. 11:50i can now take away
284. 11:54the ice bath
285. 11:59and we're going to now place a round
286. 12:02bottom flask
287. 12:04as soon as i dry the water off
288. 12:08it came out of the ice water
289. 12:14okay so this is called a thermal well
290. 12:19this one's specifically designed to fit
291. 12:21perfectly around
292. 12:23milliliter round bottom flask
293. 12:29okay
294. 12:36so i'm raising the thermal well so it
295. 12:38goes up around the round bottom flash
296. 12:42normally we would add a boiling stone
297. 12:46we now have some boiling stones we only
298. 12:49need
299. 12:49one or two and sure enough in gloves i
300. 12:53get about 20.
301. 12:57don't blame the glove for everything i'm
302. 12:58blaming the gloves for everything today
303. 13:02okay i haven't turned the heat on yet
304. 13:04i'm gonna
305. 13:05refill that joint i'm going to set the
306. 13:08entire apparatus
307. 13:11down on the side very good i'm going to
308. 13:14find if i can get one of these blowing
309. 13:16stones
310. 13:17i want one i went to that's plenty
311. 13:23okay reseal all the joints
312. 13:29again we need to have airtight seals
313. 13:32on this slab that's imperative okay
314. 13:35water running
315. 13:37joint sealed only thing left
316. 13:41is to pull some sodium hydroxide over
317. 13:43the funnel area
318. 13:45so we have some 10 sodium hydroxide
319. 13:49we're going to pour it over the top of
320. 13:50this funnel
321. 13:53so that the bubbling has to go through
322. 13:56that
323. 13:58actually we're going to use it all
324. 14:01and it's time to crank this to high
325. 14:05so this is the rheostat that controls
326. 14:07the thermal well
327. 14:08we'll turn it on what we're going to be
328. 14:11waiting to see
329. 14:12is once this starts to heat up that
330. 14:15brown gas will form
331. 14:17we're going to let the reaction run
332. 14:19until the brown gas is all gone
333. 14:21that'll basically tell us our reaction
334. 14:23is over
335. 14:25and then we can go to the quench step
336. 14:33last we're going to preheat some ethanol
337. 14:36because that's our recrystallization
338. 14:37solvent and we're going to need it to
339. 14:40help clean out the glassware so
340. 14:42what i'm going to do is i'm going to
341. 14:44warm up
342. 14:45about 50 milliliters i like to have my
343. 14:49dropper in there
344. 14:50and we're going to raise the temperature
345. 14:53to about 100 degrees
346. 14:55because we just want it warm pure
347. 14:58ethanol which is what this
348. 14:59is boils around 92 here in las vegas
349. 15:03so 100 degrees should be barely boiling
350. 15:10it's
351. 15:12it should be denatured um it's not drink
352. 15:15drinkable
353. 15:16if the denatured alcohol means they
354. 15:17added some methanol to it so you won't
355. 15:19drink it
356. 15:20just a little bit drinking methanol very
357. 15:23bad
358. 15:24so cut we're now as you can see we're
359. 15:26going to watch the brown gas
360. 15:41it looks like our brown gas is all gone
361. 15:45so we're now ready to stop the reaction
362. 15:47and quench it
363. 15:49first thing i need to do is take away
364. 15:51the heat
365. 15:52so i'm going to literally
366. 15:55lower the thermal well away
367. 16:01and when i can just drop it to the back
368. 16:04and that'll allow the finals of the
369. 16:07liquid to stop dripping
370. 16:09and go back in okay
371. 16:13now the quench step
372. 16:18involves basically just diluting the
373. 16:21strong acids that are inside the mixture
374. 16:24we're going to use about 50 grams worth
375. 16:27of ice
376. 16:28i basically filled it up just to
377. 16:33make something dark just to show you
378. 16:36this
379. 16:36so i'm going to put this behind so you
380. 16:38can kind of see
381. 16:40but i filled up the ice to just up below
382. 16:43the 100 line
383. 16:45that should give me plenty of ice for
384. 16:47quenching purposes
385. 16:49i'm going to gently turn up this reflux
386. 16:52it hasn't started boiling yet
387. 16:55and we're going to need a boiling in a
388. 16:56minute okay
389. 16:58so this is our recrystallization solvent
390. 17:01i'm going to leave that there
391. 17:02and we're going to quench the reaction
392. 17:05so if it looks like it's cooled off and
393. 17:07it stopped dripping inside
394. 17:09we then can break this first joint right
395. 17:12here
396. 17:15very carefully i'm breaking that joint
397. 17:19now some of our product is possibly in
398. 17:22here
399. 17:23we're going to do a wrench so i'm going
400. 17:25to set this gently down
401. 17:28and our first rinse will be water then
402. 17:30we're going to come back later
403. 17:32and do a second rinse when we start
404. 17:34recrystallizing
405. 17:36but let's first quench this reaction
406. 17:39so because this is so hot i'm actually
407. 17:42going to
408. 17:44hold on to the flask using uh the clamp
409. 17:48and now watch what happens inside
410. 17:52as i pour in the hot mixture
411. 17:57you see it it's immediately making a
412. 17:59fizzy noise
413. 18:03it's melting away my ice
414. 18:06as the sulfuric acid the nitric acid
415. 18:10become diluted
416. 18:12and it looks like we're actually
417. 18:13starting to form product
418. 18:15on the top you guys can see that's kind
419. 18:19of a yellow thick thing
420. 18:21that is actually our final product looks
421. 18:23pretty good so we're going to do one
422. 18:25rinse
423. 18:26of all our glassware with pure water
424. 18:30and then we'll save it later
425. 18:34and what's nice is we're just removing
426. 18:36the acids at this stage
427. 18:38so a little extra water doesn't hurt
428. 18:40going to set that to the side
429. 18:44now for this big apparatus i'm actually
430. 18:47just going to pull the top joint off
431. 18:50and i'm going to rinse straight through
432. 18:52the entire condenser
433. 18:57okay so right into my round bottom
434. 19:02and that way hopefully i will be able to
435. 19:06remove any
436. 19:07acid type molecules that stage so
437. 19:12and now i'm going to pull this joint off
438. 19:15[Music]
439. 19:18and do a rinse down through
440. 19:23here okay
441. 19:27all right now to say what i've already
442. 19:30said
443. 19:32there's a possibility of some of our
444. 19:33products stuck in this glassware
445. 19:36we will extract that later when we go to
446. 19:38the recrystallation step so
447. 19:40again i'm going to set this to the side
448. 19:42and be very careful with it
449. 19:48okay so what i've done in here
450. 19:53i basically made a soup
451. 19:57of our product in a nicholas environment
452. 20:00our product really doesn't like
453. 20:02water very well and
454. 20:06if the product doesn't precipitate we're
455. 20:08going to stir it
456. 20:09until it gums up it's almost like making
457. 20:13butter
458. 20:15usually i call this the butter churning
459. 20:17lab where you beat on the organics
460. 20:19together until they all clump up
461. 20:25okay so i'm going to try to show you the
462. 20:29bottom just a little bit
463. 20:30you see there's some solid starting to
464. 20:32form on the bottom
465. 20:34we need it to clump up as much
466. 20:37of the material out of the liquid as
467. 20:39possible
468. 20:43and so i'm just going to stir vigorously
469. 20:48just like i would if i was turning
470. 20:50better in the old days
471. 20:54and basically i'm beating the organic
472. 20:57molecules together
473. 20:58that's how a butter churn basically
474. 21:01worked as you would beat on it long
475. 21:03enough until the organic materials
476. 21:05collapse together
477. 21:06in a semi-solid you'll also notice as i
478. 21:10beat on it
479. 21:11that the solution actually seems to
480. 21:13become a little clearer
481. 21:15that's another good sign
482. 21:19that's a sign that the organics are
483. 21:21actually clumping up
484. 21:23so i'm getting a nice layer of organics
485. 21:26on the bottom
486. 21:27the solution is becoming a little less
487. 21:30cloudy
488. 21:32okay i'm now going to ice bath that and
489. 21:36do the first crude filtration
490. 21:39okay as you can see
491. 21:42most of my products clumped up it's
492. 21:44clumped up even on the strain rod that's
493. 21:46excellent that's what we want to see i'm
494. 21:48going to ice it for just a minute
495. 21:51and while it's icing in the ice bath
496. 21:53we're going to prepare
497. 21:55our buckner funnel our buckner funnel
498. 21:58works
499. 22:00by having little holes we're going to
500. 22:02put a piece of filter paper on the top
501. 22:04of it
502. 22:05to stop anything i've made your size
503. 22:09from going through the holes
504. 22:11then we'll turn on the house vacuum
505. 22:15and we're going to wet the paper down to
506. 22:18make it
507. 22:19nice and tightly bound and i don't know
508. 22:22if you can
509. 22:23see from where you're at
510. 22:26maybe i'll disconnect just for a moment
511. 22:29to illustrate this principle
512. 22:31but as soon as i pour in some water
513. 22:35i have some water from here
514. 22:39i'm on camera okay the water gets sucked
515. 22:42immediately
516. 22:42right through and that's the nice thing
517. 22:45about a nice suction filtration will be
518. 22:47a really
519. 22:48fast filtration we're going to do right
520. 22:50now
521. 22:51now the object is to remove any acids
522. 22:55and to capture as much as the organics
523. 22:58as we can
524. 23:00the other thing is we're going to reuse
525. 23:04this speaker to recrystallize in
526. 23:07so we do not
527. 23:10have to get all the solid out the only
528. 23:13thing we have to remove is all the acid
529. 23:15so what i'm going to do now
530. 23:20is just slowly pour this liquid over the
531. 23:23top of our filter paper
532. 23:31okay since we're removing the acid i'm
533. 23:34going to do one rinse of everything
534. 23:36with water
535. 23:40and i'll pour that over the top
536. 23:44okay and hopefully most of our products
537. 23:47still inside here
538. 23:49looks like we have a fair amount of
539. 23:50product
540. 23:52you may see that this is going to be a
541. 23:54good day so far
542. 23:56okay we're going to wait for this to
543. 23:58stop dripping
544. 23:59and it has stopped dripping a couple
545. 24:02more drips
546. 24:03okay it has stopped dripping
547. 24:07i can now turn the suction off
548. 24:10i'm going to show you what's inside of
549. 24:12our buchner funnel right now
550. 24:14if i can tip it over just enough without
551. 24:16spilling
552. 24:17you see some of our product is was
553. 24:19captured by there
554. 24:21we're going to transfer that back into
555. 24:22here
556. 24:24and then we're going to take
557. 24:28a scoopula or spatula and carefully lift
558. 24:32up the paper
559. 24:36and i'm going to show you the paper up
560. 24:37close and personal
561. 24:40just you see if you look carefully at
562. 24:43the paper
563. 24:44you see it's covered with yellow product
564. 24:46as well i'm going to set that just on
565. 24:48the edge of our
566. 24:50first funnel and then there's a few more
567. 24:52powders in here
568. 24:55i'm going to try to maximize our yield
569. 24:58so i want all that yellow solid in
570. 25:01back into the original beaker
571. 25:04okay now
572. 25:09this is our crude product the procedure
573. 25:13say to take a melting point of the crude
574. 25:15are we still going to do that professor
575. 25:18yeah think about the hunt
576. 25:19we'll do them together okay so i'm gonna
577. 25:22take a little sample now
578. 25:25and hopefully it'll not be too gooey
579. 25:30which is really bad it's for sure gonna
580. 25:32be back with this wet still too
581. 25:33yeah it's not gonna be a good sample i
582. 25:35usually have them dry up for a few
583. 25:36minutes
584. 25:37okay i'm gonna take this and dry it then
585. 25:40okay
586. 25:43because i normally don't do a crude
587. 25:44because it's always wet
588. 25:46yeah just let it
589. 25:49i'm gonna let the vacuum just suck on it
590. 25:51for a while
591. 25:52and then there's some crystals on the
592. 25:54corner
593. 25:56so i'm going to leave the vacuum going
594. 26:02and i'm going to take a little sample of
595. 26:04this out
596. 26:06we're going to lose a little bit of our
597. 26:08yield guys
598. 26:10there's a nice looking sample of product
599. 26:12right there
600. 26:13i'm gonna put it right on the top of
601. 26:14this put my
602. 26:17melting point tube next to it to remind
603. 26:20me to take a melting point of that later
604. 26:22okay so that's just going to be sitting
605. 26:24there grind
606. 26:26the rest of our product we're going to
607. 26:28recrystallize
608. 26:30the secret to reclassilization is the
609. 26:32following rules
610. 26:34you always want the minimum solvent
611. 26:36possible
612. 26:37to completely dissolve everything
613. 26:40now remember i said some of our product
614. 26:44looked like it was stuck in here
615. 26:46i want you to look there's some yellow
616. 26:47stuff here i have some boiling ethanol
617. 26:50which i started burrowing earlier
618. 26:52i'm going to do a little rinse
619. 26:55you see we got a nice yellow color
620. 26:59i don't want those boiling stones but i
621. 27:02want any organics
622. 27:05okay so that another little rinse
623. 27:11and my glassware almost has no yellow
624. 27:14color anymore
625. 27:15that's a good sign okay
626. 27:21so i've removed the product that was
627. 27:23stuck to that glassware
628. 27:25i'm going to do the same now to this one
629. 27:29same exact thing except we're going to
630. 27:31start at the top
631. 27:32and do a little rinse first
632. 27:36for the condenser just
633. 27:40and i'm gonna do another little rinse
634. 27:43all right i should take care of the
635. 27:44condenser
636. 27:46that means i can take this clamp off
637. 27:50set that just gently like that and look
638. 27:53carefully
639. 27:54so i'm looking to see is there any
640. 27:56yellow left on there
641. 27:57it looks pretty clean so now that leaves
642. 28:00the claisen adapter
643. 28:03last one to rinse off
644. 28:17okay so we examine the claisen adapter
645. 28:22do we have all the yellow off that one's
646. 28:24good
647. 28:25okay so we have more or less transferred
648. 28:28as much as we could
649. 28:30into the original flask
650. 28:34we are now going to recrystallize it by
651. 28:36just blowing the solvent
652. 28:39i'm going to add a little extra solvent
653. 28:42to try to dissolve the edges
654. 28:48now one of the other catches about
655. 28:50recrystallization
656. 28:51is if you use too much solvent you lose
657. 28:55part of your yield
658. 28:56so you want just enough to dissolve
659. 29:00everything but not so much
660. 29:04that you lose your product in the final
661. 29:06filtration
662. 29:08one last thing i need to rinse off
663. 29:11is the story rod you want that out of
664. 29:13there
665. 29:14so you see the steering rod is still
666. 29:16sticking
667. 29:18let's get all our product right off that
668. 29:20stirring rod
669. 29:23come on strain rods let go
670. 29:27there it goes a little bump there so we
671. 29:31have a nice clean strain run
672. 29:33okay let's see if we can make this boil
673. 29:38now and go
674. 29:39completely clear should be a nice
675. 29:42yellow clear color
676. 29:48set that down and that'll usually
677. 29:51take a few minutes and now i'm going to
678. 29:54go back and check on our crude
679. 29:56as it dried long enough
680. 30:00can't drive with acetone or it will
681. 30:03i think we have it dry enough in here to
682. 30:05get a melting point i'm going to try
683. 30:16okay it looks like i have enough of a
684. 30:19crude sample
685. 30:21if we bounce it to the bottom we should
686. 30:23be able to obtain a melting point
687. 30:26that said i want to increase
688. 30:30my overall yield
689. 30:37yeah i think that's enough for a melting
690. 30:39point okay
691. 30:41so i have the the product in here we're
692. 30:44going to send this to the melting point
693. 30:45wrap around us a little bit later
694. 30:53and so while that's trying to dissolve
695. 30:57i'm going to transfer what
696. 31:00again anything that's in here
697. 31:04oh there's still a little bit inside i'm
698. 31:05gonna try to get it in here
699. 31:07again the whole goal is maximum yield
700. 31:09highest purity
701. 31:11so
702. 31:16let me show you one more cool trick you
703. 31:18can do
704. 31:24no that wasn't it okay
705. 31:27normally when the paper is wet
706. 31:30you can get it to stick to the glass
707. 31:32there we go that's what i was hoping for
708. 31:35okay so i made the filter paper
709. 31:39stick to the glass
710. 31:43and i'm going to try to squirt off as
711. 31:45much of the yellow
712. 31:47as will come out easily
713. 31:51so okay
714. 31:56that looks like enough of that
715. 31:59oh okay i'm going to show you this
716. 32:03just to get up close the orange we don't
717. 32:06want but
718. 32:07it looks like i got most of the yellow
719. 32:09off but i missed some of it there
720. 32:10we're just going to call that a little
721. 32:12bit of wash maybe
722. 32:14not very much might be a few milligrams
723. 32:18okay our liquid here looks like this is
724. 32:21about to boil
725. 32:24and to see if we have enough solvent
726. 32:27i'll show you a trick
727. 32:29we're going to put a watch glass on top
728. 32:32a little bit of ice
729. 32:34and if it boils and re-condenses
730. 32:38all of the edges should be dissolved
731. 32:41down into the bottom
732. 32:44and that's what we're going to do right
733. 32:45now you see how it's boiling
734. 32:53and there went one section of the edges
735. 32:58let's spin it around slowly we're
736. 33:00looking for
737. 33:01anything stuck on the sides of the
738. 33:03beaker
739. 33:05because while it's boiling
740. 33:10it'll dissolve away while we're
741. 33:12reflexing the liquid
742. 33:14oh it's looking pretty good i want to
743. 33:18mention that you're boiling ethanol
744. 33:19right
745. 33:20yes yeah so uh if you ever have to boil
746. 33:22ethanol in the lab you should always
747. 33:23keep it covered or on a fume hood
748. 33:25because you can get drunk off the vapors
749. 33:28yep true that which is a sad truth
750. 33:33for some okay so
751. 33:37as i go around i'm going to go around
752. 33:39one more time
753. 33:40and you guys watch see if you see any
754. 33:42solid still stuck on the sides
755. 33:45i'm not look seeing any um
756. 33:50maybe right there or those might be on
757. 33:53the outside
758. 33:56okay it looks like we've done enough
759. 34:01the liquid is basically clear
760. 34:05so the other key about recrystallization
761. 34:07is be very
762. 34:08patient cooling it off if you cool it
763. 34:11off too fast
764. 34:13the products when the crystals form
765. 34:16will actually trap products in
766. 34:19and i can see it's already starting to
767. 34:21form crystals on the bottom
768. 34:24i don't know if i can tip it you want to
769. 34:26tip the camera
770. 34:28yeah you turn it so the text is that way
771. 34:33okay yeah there's a little bit of
772. 34:36crystals for me
773. 34:38once you have the first crystals the
774. 34:39other crystals should grow on them
775. 34:43and i can see them in a pile when i do a
776. 34:45swirl
777. 34:47i can't see it when i take the blue away
778. 34:49though
779. 34:50okay so i'm going to try to show you up
780. 34:53close
781. 34:54but you see there's a little pile of
782. 34:56crystals starting to form in the bottom
783. 34:59hopefully you can see that
784. 35:02and so we're going to just let that cool
785. 35:05it needs to come down to room
786. 35:07temperature
787. 35:08and before we ice it the entire beaker
788. 35:12should fill up with crystals
789. 35:15then you're going to do a final we'll do
790. 35:17a final icing
791. 35:20to maximize our yield in this solvent
792. 35:23so for now we're just cooling
793. 35:29and while that's cooling
794. 35:32i'm going to prepare the second
795. 35:34filtration
796. 35:35so our final filtration we need to clean
797. 35:39this up
798. 35:41i'm going to remove all the acid water
799. 35:44that's in here
800. 35:46and then rinse it out with acetone
801. 35:48because our final filtration will be
802. 35:49organic
803. 35:50and the organics need to be discarded in
804. 35:52the organic waste
805. 35:54it does this thing sometimes where it
806. 35:56emulsifies instead of crystallizes
807. 36:00okay guys we're getting we're been
808. 36:03recrystallizing
809. 36:05you'll see we got a nice pile of
810. 36:06crystals right now
811. 36:08soaking on the bottom we feel the
812. 36:10temperature
813. 36:11fills more or less to room temperature
814. 36:13we're now going to
815. 36:14ice it for five more minutes and do our
816. 36:18final filtration
817. 36:19after five minutes okay
818. 36:22we've iced our final product we have a
819. 36:24nice clumped up here on the bottom
820. 36:27the final filtration needs to be done in
821. 36:29ethanol so over here i prepared
822. 36:32some ice cold ethanol also in an ice
823. 36:35bath
824. 36:36we're going to first wet down the paper
825. 36:38with ice cold ethanol i wetted
826. 36:40the suction's on check wet the paper
827. 36:43down
828. 36:45check suck the ethanol through really
829. 36:48fast
830. 36:49okay now we're going to try to transfer
831. 36:53all of this liquid in one go
832. 36:56and then capture the solid
833. 37:00on the middle of filter paper
834. 37:03if there's any left behind we're going
835. 37:05to use ice called ethanol but remember
836. 37:06the more
837. 37:07ethanol i use the more the product will
838. 37:10be lost
839. 37:12so we're in a catch-22 we want to
840. 37:14transfer it all
841. 37:16we don't want to lose anything
842. 37:19and since it all stuck to the top
843. 37:22i'm going there it goes come out
844. 37:28i'm about to get us my glass steering
845. 37:34rod
846. 37:36you're just hanging out upside down okay
847. 37:39so some of it's stuck to the bottom i'm
848. 37:41afraid of that i don't want
849. 37:43to lose too much product but i want my
850. 37:45product
851. 37:47for the final weight
852. 37:50okay so most of it came out but not all
853. 37:53of it
854. 37:54that's what the ethanol is for i'm gonna
855. 37:56squirt it
856. 37:58swirl it pour it how do we do on that
857. 38:01one
858. 38:01we got about eighty percent we'll do it
859. 38:04one more time
860. 38:05squirt squirt maybe two more times
861. 38:14now i'm
862. 38:23let's pour some more ethanol
863. 38:30okay so this will be my final one
864. 38:36i hope pour it over the top
865. 38:40okay a little bit of products lost
866. 38:44can't quite transfer it all um
867. 38:48but if i look down at my separatory
868. 38:49funnel that looks really good
869. 38:51i get a nice view of that and we're
870. 38:54going to do
871. 38:55one wrench now of
872. 38:58ethanol across the top and hopefully
873. 39:01that'll remove
874. 39:02any of the impurities that may have been
875. 39:05created
876. 39:06which you'll learn in the pre-lab is the
877. 39:08two
878. 39:10initial products can be our impurities
879. 39:13now sometimes if you get a lot of the
880. 39:15other products your your solution down
881. 39:17here will be really bright orange
882. 39:20okay now take a picture of the solution
883. 39:22you see that yellow color
884. 39:24technically speaking if we condensed it
885. 39:26down we could make
886. 39:28more crystals out of the ethanol here
887. 39:30but we're not going to do that today
888. 39:31our yield will be just whatever we
889. 39:33obtained from up here
890. 39:34so now that we've done the rinse and
891. 39:36it's ethanol it's going to take
892. 39:3815 minutes of air drying time we're
893. 39:40going to stop recording and just let the
894. 39:43vacuum go
895. 39:44okay we have been drying our product for
896. 39:47about 15 minutes
897. 39:49you'll notice two things one our product
898. 39:51is dryer
899. 39:53but remember what i said about reese
900. 39:55dissolving some of the solid
901. 39:58about half of the liquid evaporated away
902. 40:01and some of our lost product is now
903. 40:03crystallized on the bottom
904. 40:06as i said if we wanted to we go back and
905. 40:09try to collect that but
906. 40:10we're not going to
907. 40:14you sure you mentioned sources of waffle
908. 40:15or product in your report
909. 40:17make sure when you're explaining the
910. 40:18percent losses
911. 40:20you know one of them's right there that
912. 40:23always happens remember
913. 40:25what i said earlier in the lab the more
914. 40:26ethanol the more of your product ends up
915. 40:29down in this funnel
916. 40:30now our product here is nice and dry in
917. 40:34a nice
918. 40:34light yellow solid we're going to put it
919. 40:37on our pre-weighed beaker
920. 40:40that we pre-weighed at the very
921. 40:41beginning
922. 40:43so it's looking really pretty
923. 40:46it's nice and white i'm going to gently
924. 40:50knock off any of the
925. 40:53powder that was on the paper we're going
926. 40:56to discard the paper because
927. 40:58you never weigh paper because liquid
928. 41:01impurities always get stuck inside the
929. 41:02paper
930. 41:04check inside of here a little bit of
931. 41:07crystals right there
932. 41:12so once we are confident
933. 41:15we retain as much product as we can and
934. 41:18again i know we've lost some over here
935. 41:20in the
936. 41:20in the sidearm class we're now going to
937. 41:23do our final reign for today
938. 41:25and then i'll take a melting point to
939. 41:28this final product
940. 41:32we pre-weighed this watch glass we now
941. 41:36have our product on it
942. 41:38and if i drop it it's all because of the
943. 41:40gloves
944. 41:43yeah yeah yeah i couldn't feel for sure
945. 41:47okay
946. 41:48so when that's
947. 41:51right there there we go yeah 55.553838
948. 41:58the last thing we need is a small sample
949. 42:00for the melting point
950. 42:02we just use this the other beauty of a
951. 42:05watch glass
952. 42:06gives us a nice surface to
953. 42:09put our product in yep
954. 42:15and our product is fairly dry we just
955. 42:18need to bounce it so where did the
956. 42:19bounce tube go
957. 42:21over here
958. 42:26so we use the glass too to balance it it
959. 42:28helps pack the tube
960. 42:30here we're going to put the glass on the
961. 42:33top
962. 42:34and as we let go you'll see that the
963. 42:38the melting point tube bounces and it
964. 42:41condenses the solid on the bottom we'll
965. 42:43do it again so we can get that
966. 42:44ready you can see it bouncing in there
967. 42:49there we go and we now have a sample
968. 42:53that's ready for a melting point okay
969. 42:56let's move over to the melting point
970. 42:57apparatus i got it
971. 43:02okay everybody i'm getting uh to set up
972. 43:04here to uh get the melting point
973. 43:06of the crude and the purified product
974. 43:09uh on the left i went ahead and put the
975. 43:12so the left one here is the crude uh the
976. 43:15right one here is the pure
977. 43:17i set my starting temp to be 40
978. 43:20and then the ramp rate you know is
979. 43:22typically 5 degrees
980. 43:23c per minute and the stop turn of the
981. 43:26matter it's going to melt well before
982. 43:27the stop tap i think it's like 2 30. so
983. 43:29yeah well before then it's going to melt
984. 43:31but enjoy the show
985. 48:31you