Sciencemadness Discussion Board

Is this right?

APO - 13-9-2013 at 18:27

This video says it will form Acetamide upon evaporation, so what reaction is taking place here? To me it seems like it should form Ammonium Acetate and Ethanol, so if it really does make Acetamide, what's the stoichiometry?

Mailinmypocket - 13-9-2013 at 18:58

Check this out, might be helpful.

AndersHoveland - 13-9-2013 at 21:23

You are indeed correct, it should mostly form ammonium acetate and ethanol. However, if all the water was used up, or perhaps preferentially drawn into the ammonium acetate layer (it is hygroscopic), this could possibly leave an excess of dry ammonia, which would indeed react with ethyl acetate to form acetamide.

The ethyl acetate will hydrolyze at a much faster rate with the hydroxide ions in equilibrium than with NH3.

I had been thinking about this myself, wondering if any traces of acetamide could be formed by reacting concentrated NH4OH with ethyl acetate.

Normally ammonium acetate has to be heated under flame in a sealed tube for acetamide to form. I believe you will find some old references to alcoholic ammonia reacting with ethyl acetate also.

[Edited on 14-9-2013 by AndersHoveland]

Endimion17 - 14-9-2013 at 11:56

Ethyl acetate and ammonia will yield acetamide, but the reaction is very, very slow not only because ammonia is a rather poor base, but also because those two chemicals aren't miscible. It's a bit like oil and water. Surface area can be increased by agitation, but the rate of reaction is still pathetic.
I've read somewhere it takes days under agitation before you get appreciable yields. Acetamide in solution works as a solvent for ethyl acetate, so even after the mixture becomes only one phase, you still have to wait for the yields to climb up.

Maybe the best solution would be to mix the chemicals with surplus ammonia, close the container and just leave it for a month. That should do the trick.

Magpie - 14-9-2013 at 12:33

I have done this synthesis with good results. I don't have access to my notebook right now but IIRC my procedure said let it sit until the next lab period, which would be ~ 3 days.

[Edited on 14-9-2013 by Magpie]

APO - 14-9-2013 at 12:43

Thanks everyone. Also, regarding Acetamide, Wikipedia says dehydration of it results in Acetonitrile, how would it be dehydrated in order to give Acetonitrile?

12AX7 - 14-9-2013 at 13:49

Heating or concentrated sulfuric acid? Should be a reference in any synthesis related to those chemicals. Try Orgsyn?

Tim

APO - 14-9-2013 at 14:02

I looked up Acetonitrile on Orgsyn, but only procedures which require it appeared, none which depicted the synthesis of Acetonitrile, except for it's esters and halogenated derivatives.

12AX7 - 14-9-2013 at 14:07

Heating or concentrated sulfuric acid? Should be a reference in any synthesis related to those chemicals. Try Orgsyn?

Tim

Magpie - 14-9-2013 at 17:04

Acetonitrile is made by dehydrating with P4O10.

APO - 14-9-2013 at 21:10

Anything domestically available, or easier to come by, such as H2SO4?

Magpie - 16-9-2013 at 11:09

Quote: Originally posted by Magpie  
I have done this synthesis with good results. I don't have access to my notebook right now but IIRC my procedure said let it sit until the next lab period, which would be ~ 3 days.

[Edited on 14-9-2013 by Magpie]


Brewster (Unitized Experiments in Organic Chemistry,1960), says to let it stand for at least 48 hours.

Letting it stand for 48 hours my yield was 25.5g, or 85%.

AndersHoveland - 16-9-2013 at 11:48

Quote: Originally posted by Endimion17  
the reaction is very, very slow not only because ammonia is a rather poor base, but also because those two chemicals aren't miscible. It's a bit like oil and water.

Maybe that's why an alcoholic solution of ammonia is used.
Ethyl acetate is miscible in ethanol.