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Topic: chloracetaldehyde....need help ASAP  (Read 3081 times)

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Offline ivanakaj

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chloracetaldehyde....need help ASAP
« on: January 13, 2010, 07:53:59 AM »
Hi!
I'm wondering why is chloracetaldehyde only available as a water solution.....i'm donig a reaction, where i need it unhydronious, and have removed water thorough column distillation....now i want to know if it will remain stable until tomorrow, when i would star my reaction.

so i need to know the role of the water in it???

thnx

Offline stewie griffin

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Re: chloracetaldehyde....need help ASAP
« Reply #1 on: January 13, 2010, 08:07:47 AM »
I doubt it. From the Encyclopedia of Reagents for Organic Synthesis (a book you should get comfy with if you're going to do orgo research):
This molecule is "highly prone to polymerization, should be used immediately after preparation." It also states that water-free choloracetaldehyde can be prepared by periodate oxidation of alpha chlorohydrin (JACS 1945, 67, 688).
I imagine that if you distilled it you may have either polymerized the compound or just made the hemiacetal. One good way to find out when you have the question of "is my reagent any good" is to take a quick proton NMR tomorrow before you get going. If it looks like it should, then use it. If not, then don't.

Offline ivanakaj

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Re: chloracetaldehyde....need help ASAP
« Reply #2 on: January 13, 2010, 08:22:54 AM »
We don't have a t the lab.....we have some older books with reagnets, but they didn't contain this reagent. The thing is i'm afraid it will polymerize until tomorrow....so i'm going to add the reagents and let it sit like this over the night, hopeing that they will react with each other rather than with itself.

i don't understand why it's kept specifically in water....and i now have it in chloroform, maybe it too will slow down the polymerization....i doubt that...but it's worth the chance.

there is no way that i can distile the water away and put up a 6 hour reflux reaction in one day....unless i sleep here...with is not a nice prospect.... :)

Offline stewie griffin

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Re: chloracetaldehyde....need help ASAP
« Reply #3 on: January 13, 2010, 08:42:31 AM »
Chloroform is slightly acidic so it may lead to polymerization. I really don't know as I've never worked with this.
If your strapped for time, maybe next time instead of doing to slow/tedious distillation, just use a heat gun instead of a hot plate. You can get that stuff distilled much faster that way. It's a bit sloppier but even for sensitive stuff I have sometimes been able to get away with a 30 min max distillation.
Good luck.

Offline orgopete

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Re: chloracetaldehyde....need help ASAP
« Reply #4 on: January 13, 2010, 12:20:48 PM »
Do you have to dehydrate it first? Can you just react the hydrate with your nucleophile and drive the water out of that with a water trap? If we knew what kind of reaction you were attempting, we could anticipate that or even possibly offer alternatives.
Author of a multi-tiered example based workbook for learning organic chemistry mechanisms.

Offline ivanakaj

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Re: chloracetaldehyde....need help ASAP
« Reply #5 on: January 16, 2010, 12:55:57 PM »
it needs to be completely anhydrous, and chloracetaldehyde can't be bought outside a water solution....i want to make a phosphorane for another reaction. i belivie that i didn't pput the aparature for distillation good, and that's why it was so slow.

i'm trying it again this week...hope that the distillaion will go faster, so i can do the reaction in the same day.


i want to thank you all for your help and advice. :)

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