Organic Chemistry Lab: Recrystallization
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- เผยแพร่เมื่อ 7 ก.ย. 2024
- A demonstration of the technique of recrystallization used in Organic Chemistry labs.
Demonstrations conducted by:
Dr. Scott Allen
Assistant Professor, Chemistry/Physics, University of Tampa
Directed by:
Gordon McClelland
Computing and Information Services, Vassar College
Produced by:
Cristian Opazo
Academic Computing Services, Vassar College
Production Assistants:
Ken Bolton and Steve Taylor
Academic Computing Services, Vassar College
Post-production by:
Becca Marcus
Vassar College, class of 2008
and
John Santos
Vassar College, class of 2007
Thanks to Ed Wroblewski, Film Department, Vassar College
Copyright © 2007, 2008 by Vassar College.
Do not reproduce, download or edit without permission.
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Holy crap! I know this guy and let me tell you he is the best biology teacher I have ever had and is just the nicest, kindest and most patient professor/ human I have ever met.
I am in university now far away from where this guy works but man this video makes me miss his class and him in genral.
what school?!
Wha it's solvent
Damn! I wish I would have watched this BEFORE I went to lab!
I had no idea what the hell was going on.
Great video
OMG thanks sooooo much, my freaking teacher doesnt freaken tell you how to do anything thanks so much, finaly someone who understands, thank god for you, what would all us youtubers in chermistry do without you seriously
Believe me, we did try a lab coat, but the studio lights were so intense that our instructor shone like a fluorescent bulb, ruining the whole frame. We tried *three* different shirts until we decided to go with this very unprofessional-looking shirt, which worked the best with the lights.
My university doesn't require lab coat OR gloves. I don't even think it's allowed ...
I don't know why you guys do these videos, but thank you. It helps A LOT to see these experiments performed BEFORE lab.
I'm performing this lab tomorrow and this clears up a lot of ambiguity before I start the lab and just being thrown into it. Thank you !
Great video! This is my first semester of Ochem lab, so I'm really nervous... I have a teacher with a reputation of being obscenely strict, so I'm trying to get ahead so that I can be competent when the time comes ... Thanks for the video, It's very clear cut and easy to understand!
Your videos are the most helpful I've found, thank you!!
no lab coat?
-10!!
haha at my university I wouldn't even be allowed to enter the class
Super helpful video. Thanks mate!
sups helpful! im taking chemistry online & would be sooo lost without youtube videos like these! thanks
amazing video, this really helped me since my lab is fully online now. THANK YOU!
Hod do you have Ochem online? Virtual labs, mailed equipment, or what? Sounds rough if not hands on or so.
Anthony Rodriguez for ochem 1 I would have to watch a video of someone else doing the experiment and now for ochem 2 I have to do the experiments through an online software where you pick up chemicals and put them in virtual containers and stuff.
@@kassyg3897 wow, these covid restrictions are ugh for their results. I took Ochem 1 a year ago and just couldnt imagine what you just said you do for the work for class. Hands on seems better but still learning at the end of the day. Good to know
very helpful, wish i'd seen this before i fucked up in labs the other day by adding way too much solvent!
Thanks to you, i understanding the lab so well that i breezed through it without error and my lab was very successful. keep putting up more videos as it is very insightful and helpful. also do you have labs for any other subjects.
This video shows you how to do it the long, complicated, unnecessary way. All you have to do is remove the lighter from underneath and you get recrystallization. It's that easy. "Hands on" is always the best way to learn anything
It is, the purpose of putting it into the ice bath is just to get more precipitate. Usually it isn't such a good idea, depending on the solvent and what compounds you have in solution. It was okay in this experiment because he probably formed the compound with nitric acid and sulfuric acid (hence, nitrated benzoic acid). In which case, nitric acid and sulfuric acid are completely soluble in water, so they will remain in solution regardless, but precipitate the crystals.
great instructional video, helped me understand the recrystallization process much better
im on my way to clandestine chemistry , fuck going to university ! the internet is truly a remarkable tool ,
HamNediaj
Dats right👍
Good video, easy to understand. Already did all my ochem classes but for some reason I still enjoy it :P
LOL for my recrystallization lab, started out with .46g, ended up with 0.04g. Worst part was I needed it for the next lab xD. I cannot express my hatred for ochem lol
Hmm, not too sure about this as all you have done is
dissolve the solid and then recrystallize it without filtering out the solid
impurities and then separately filtering away the soluble impurities in the
second stage. A simple method to purify by recrystallization: dissolve crude
product in the minimum of a suitable HOT solvent, promptly filter through a hot
Buchner (thus removing insoluble impurities), allow to SLOWLY fully
recrystallize, maybe cool if required, re-filter in a fresh Buchner ensuring
whole surface of paper is covered in pure solid, gently pack-down to ensure
maximum drying effect of airstream, recover, air-dry, weigh and do MPt
determination. For a higher level of purification activated charcoal is used in
the first solution stage to absorb more impurities.
I can't tell, did you cap and cool the mixture like you are supposed to do ? SO HAPPY to see you are not recrystallizing in beaker like some knuckhead instructors do.
Thank you once again
Amazing video , thank you!
This is very helpful, Thank you. You are better than my teacher!!!! Lol
Very impressive
Love the video, very comprehensive and well explained!
"Every time you come for practical you need to have your labcoat, safety googles and proper gloves. Otherwise, you will not be granted access", says my lecturer for every practical.😂😂
Ker sley must be nice... our lab doesn’t give us gloves or lab coats :)
Very well explained thanks !
A very good video👍🏻👍🏻thank u
I'm getting into this. Thanks
I hate it when that happens. I'm glad you appreciate our eyes. :)
thanks
Very good video! Could you if it is not a problem to explain the process of purification and recrystallization of kclo3 obtained from sodium hjpochlorite! Thank you in advance!
Thanks, i am going to do this lab and i am sure i wont make mistakes.
With video's like this, poeple don;t even have to go to school, the future is here.
I prefer reflux condenser and recrystallisation over night in the oil bath.
Omg this was sooo helpful. Thank u so much! =D
This was helpful video.....
thank you!
Thanks a lot!
Thank you so much!!
The amount of solvent to use really is not a judgement call as you can determine a very close measurement simply by looking at solubilities.
Robert Klepper not if your compound is an unknown. And I just noticed that you commented this a decade ago (nearly). Lol
dude you rock!!
Thanks!
so the impurities remain dissolved in the solvent? what type of organic solvent should we use if the compound we want is not water soluble and should be harmless if consumed?
The solution is filtered and washed with cold solvent to remove the solvent soluble impurities that were removed during the crystallization. They just didn't show that step.
Vacuum filtration is pretty noisy and probably doesn't make good video material, I suppose.
Could you explain about two solvents to recrstaltion
are u from wild n out
@1Project1Haiduc1 it sounded more like the bottom was wet when it hit the hot surface
Unless I missed it, I didn't hear a description of exactly WHAT was being recrystallized
I'm not familiar with vacum filtration, is there an easier way to remove the crystals?
is it better to use a steam cone instead of a hot plate to heat the solution?
is boiling point when you see bubbles but not roll? what about when bubbles start to rise is that to fare?
Sem micrografias fica difícil avaliar a recristalização.
Why are the impurities more soluble than the desired material? Does that have to do with the solvent used and knowing what typical impurities are?
Steven Ingersoll by selecting a solvent that will dissolve the majority of chemicals, by checking their solutes, you can deal with other impurites with a different solvent later.
Will slowly taking the solution down in temperature instead of removing from the hot plate entirely slow the recrystalization process and capture less impurities, or is it best to allow the solution to cool to room temp as shown in the video?
I've seen both done. My guess is that the former will produce the best results, but will be much more work and time intensive.
i like how i found this out right after my ochem lab final.....:T
how do you know how much solvent you are adding?
How to prepare benzoin
Min 5 method to prepare it
I don't think taking the temp down slowly would be helpful. It seems to me you would lose more solvent by doing that which would trap impurities due to a quicker crystallization. Someone correct me if I'm wrong..
What was the substance used in the video ?pliz
How do you test the purity of the recovered crystals?
Measure the melting point range of your recovered crystals and then compare your measured range to the known literature melting point range of that compound. If your measured range is lower, then your compound is still impure. If your measured range is about the same as the known literature range, then your product is pure.
Did I just hear the Erlenmeyer flask crack at 4:30?
How do we calculate recovery?
dude,where is your lab gown?
Could anyone explain the use of wooden stick and bumping phenomenon? Thanks
You need something irregular shaped in the solvent so it provides nucleation points for the vapour bubbles. The wooden stick is a porous material - if you place it in near boiling water you can see tiny bubbles forming on it.
He used it because of the little volume of solvent but for larger vlumes, magnetically stirring the suspension will also work to even out the boil and distribute heat.
Krist novaselic
crystallization is black magic
I dont understand, the impurities will still be in the erlenmeyer. How come it is more pure
Why dont you recrystallise by heating at reflux?
Theoretically, reflux does not allow solvents to evaporate from the system, i.e. the amount of substance per volume of solvent (concentration) does not change.
But in the case of recrystallization, we have to evaporate the solvent so that the compound reaches its solubility limit (...and goes beyond the limit at high temperature). And then we cool the solvent so that the compound crashes out of the solution as crystals.
You forgot to add blue food coloring...
not necessary
I want to learn
what are you recrystallizin
@aokka
Those aren't chemists. A chemist knows the reasoning behind the steps he uses. He doesn't merely play "monkey see monkey do" for quick monetary gain.
Using recrystallization will decrease the yield of reaction right?
No, recrystallization is a separate stage after the reaction has been completed, hence it doesn't affect reaction yield but it does of course reduce overall yield of the whole process.
Average quality NN-DMT < 99.8% pure NN-DMT. Quality over quantity all day.
I mean, just as an example.
You should have passed that solution through the filter paper
0:19 - ARHHH THE THE THE LOOL
@scivislab thats because of the black background you are using. Its all about quantum wave mechanics bro... its all about quantum wave mechanics.
same purpose as boiling chips.
I'm usually on the other side of these tables lol
8:15, hey dude, solVENT will never recrystallize, it's the solUTE....
such an important distinction, thank you so much for your service.
One step is missing
why does my recrystallization result in all the solution turning to crystal without excess solvent to decant?
it is hot and has dissolved all the solid powder but when it finishes cooling it is all crystal so where do the impurities go?
I must be doing something wrong...
Use more solvent. What is your starting material and NP solvent? I might be able to help.
@@jindy3677 they might have graduated already
@@mishaldurrani125 lmao fr
thanks Jerry Seinfeld!
did this and made aspirin
*methamphetamine
metalhead33
N,N-Dimethyltryptamine
2021 anyone?
ah i see ok ^^
8 people couldn't crystallize their MDMA