Sciencemadness Discussion Board

A lot of acetonitrile.

Reduce-Me - 2-4-2010 at 07:25

So, I'm starting to get a ton of acetonitrile and I'm curious to know what I could do with it besides using it as a solvent.

Any ideas?

Nicodem - 2-4-2010 at 10:05

The "I'm starting to get a ton of acetonitrile" sounds very much like you are getting used HPLC acetonitrile/H2O mobile phase from some analytical lab that does not recycles it. If this is the case you should know that it is not so easy to get dry acetonitrile as distillation gives the acetonitrile/water azeotrope (86% w/w).

As for what you could do with it, you should first define your interests and limits. You can make a lot of things from acetonitrile: ethylamines by hydrogenation (ethylamine, diethylamine and triethylamine), acetamide by hydrolysis, aryl methyl ketones via either the Hoesch reaction or addition of arylmagnesiums, alkyl methyl ketones via alkylmagnesiums addition, N-benzylacetamides and N-t-alkylacetamides via the Ritter reaction, you can use the acetonitrile/H2O2 reagent for epoxidations of alkenes...

Check the attached entry on acetonitrile from e-EROS for more ideas.

[Edited on 2/4/2010 by Nicodem]

Attachment: e-EROS_Acetonitrile.pdf (79kB)
This file has been downloaded 6414 times

unionised - 2-4-2010 at 10:48

IIRC you can break that azeotrope by saturating it with salt. It splits into two layers. The separation is better if you get the stuff ice cold.

Melgar - 2-4-2010 at 11:30

Apparently you can reduce it with tin chloride in dry ether to get acetaldehyde. Or use it in Grignard reactions to make methyl ketones. You probably need to get it quite pure for those reactions though.

vulture - 2-4-2010 at 13:14

Drying acetonitrile is a MAJOR pain. Not to discourage anyone, but think about your requirements, i.e. how dry it needs to be. A few colleagues of mine spent the better part of two weeks trying to get acetonitrile dry enough for electrochemistry. That is, dry enough not to see the characteristic reduction/oxidation of water in a voltammetry experiment which limits the potential to 1,2V IIRC.

IIRC, drying with P2O5 or CaH2 seemed to yield sidereactions, but I'd have to ask them.

There should also be a section about this in "The Purification of Laboratory Chemicals" which is an extremely useful book for other aspects of chemistry anyway.

UnintentionalChaos - 2-4-2010 at 16:03

Quote: Originally posted by vulture  
Drying acetonitrile is a MAJOR pain. Not to discourage anyone, but think about your requirements, i.e. how dry it needs to be. A few colleagues of mine spent the better part of two weeks trying to get acetonitrile dry enough for electrochemistry. That is, dry enough not to see the characteristic reduction/oxidation of water in a voltammetry experiment which limits the potential to 1,2V IIRC.

IIRC, drying with P2O5 or CaH2 seemed to yield sidereactions, but I'd have to ask them.

There should also be a section about this in "The Purification of Laboratory Chemicals" which is an extremely useful book for other aspects of chemistry anyway.


Did they consider electrolysis itself as a means of drying the material? If you run some decent amperage into the mix (and presumably bubble dry N2 through the liquid to remove dissolved gases, eventually you run out of H2O to turn into gas. Sure, it's impractical for large volumes but how large was the vessel they were running this in?

unionised - 3-4-2010 at 02:21

That's odd. Normally drying solvents that form an azeotrope is easy, you just fractionate out the water. Keeping them dry is another matter.
BTW, acetonitrile reacts violently with H2SO4 so don't try it as a drying agent.

Reduce-Me - 3-4-2010 at 15:28

Quote: Originally posted by Nicodem  
The "I'm starting to get a ton of acetonitrile" sounds very much like you are getting used HPLC acetonitrile/H2O mobile phase from some analytical lab that does not recycles it. If this is the case you should know that it is not so easy to get dry acetonitrile as distillation gives the acetonitrile/water azeotrope (86% w/w).

As for what you could do with it, you should first define your interests and limits. You can make a lot of things from acetonitrile: ethylamines by hydrogenation (ethylamine, diethylamine and triethylamine), acetamide by hydrolysis, aryl methyl ketones via either the Hoesch reaction or addition of arylmagnesiums, alkyl methyl ketones via alkylmagnesiums addition, N-benzylacetamides and N-t-alkylacetamides via the Ritter reaction, you can use the acetonitrile/H2O2 reagent for epoxidations of alkenes...

Check the attached entry on acetonitrile from e-EROS for more ideas.

[Edited on 2/4/2010 by Nicodem]


It is from an HPLC lab that does not recycle it. But The stuff I have usually has 1-5% impurity.

Either trifluoroacetic acid, methanol etc. Nothing I have gotten has water in it yet.

I kind of want to venture a reaction to add two carbons with the KOH via the method from orgsyn

http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv7...


cool "paper" by the way, thanks!

[Edited on 3-4-2010 by Reduce-Me]

vulture - 7-4-2010 at 10:15

Quote:

That's odd. Normally drying solvents that form an azeotrope is easy, you just fractionate out the water. Keeping them dry is another matter.


That's not enough in this case. Alot of water can hide in apparently "dry" acetonitrile.

peach - 30-4-2010 at 19:41

Vacuum distillation?

Works for alcohol. I mean, it breaks the azeotrope.

As for uses, I can't help much there. Maybe start making your own line of lab gloves? :P

zed - 5-5-2010 at 22:41

Can the water be frozen out? Low freezing point for acetonitrile.....-43C?

Melgar - 7-5-2010 at 18:39

There isn't any simple way to turn it into HCN, accidentally or otherwise, is there? Mostly looking at it from a safety standpoint, but it doesn't seem thermodynamically favored. Maybe burning it in a low-oxygen atmosphere could do it? CH3CN + O2 = CO2 + H2O + HNC? But I don't remember seeing that on the MSDS.

[Edited on 5/8/10 by Melgar]

zed - 10-5-2010 at 03:56

Turn it into HCN? The human body can do that, but only slowly. Quite a few folks have been exposed to acetonitrile on the job, and later died at home. Delayed reaction. But, it does take a fair amount to do the trick.

Fortunately, as nitriles go, acetonitrile is reported to be less toxic than most.

Still, it isn't water, ethanol, or mineral oil..... If you slosh a few hundred ml of acetonitrile on your tennis-shoes, it behooves you to take prompt action.

The LD 50 is about 2.5 grams/KG....Not terribly toxic, to most folks, under most conditions.