Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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acetonitrile
Yesterday I prepared a small amount of acetonitrile using the method in Vogel's 3rd (forum library). This method uses P4O10 to dehydrate acetamide.
This is not a cost effective way to make acetonitrile. But not having any experience with either P4O10 or acetonitrile, I did the synthesis just for
education and fun.
4CH3C=ONH2 + P4O10 ---> 4CH3CN + 2H4P2O7
Vogel makes a big deal out of how to get the P4O10 into the flask quickly, as it rapidly absorbs atmospheric moisture. This is most assuredly true,
and is the only real challenge to the synthesis IMO. As indicated in the procedure P4O10 will char paper. This is shown in this picture:
There is a fair amount of foam formed during the reaction but the freeboard in a 250mL RBF is sufficient so it is not a problem. Below is a picture
of the reaction apparatus at the finish. The residue consists of some char and a viscous liquid composed principally of pyrophosphoric acid.
My yield was rather low at 5.9g. I have no idea why. Expected yield was 10g.
Questions, comments, and suggestions are welcomed.
[Edited on 26-9-2013 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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kristofvagyok
National Hazard
Posts: 659
Registered: 6-4-2012
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I have prepared trifluoroacetonitrile and heptanedinitrile on the same way. It's a good method, works fairly good, the only problem was that a lot
gunk was formed during the reaction and if a cheap nitrile is made, than it is not really cost efficient.
My reaction with the CF3CN looked like this:
The recieving flask was cooled with nitrogen to condense the nitrile.
I have a blog where I post my pictures from my work: http://labphoto.tumblr.com/
-Pictures from chemistry, check it out(:
"You can’t become a chemist and expect to live forever." |
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