Author Topic: Simple synthesis of aliphatic nitriles  (Read 689 times)

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Ziqquratu

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Simple synthesis of aliphatic nitriles
« on: September 24, 2003, 02:26:00 AM »
OK, thanks go out to BASF over at

http://www.sciencemadness.org

.  I couldnt see this on the Hive, but forgive me if it's redundant. 

Patent GB464106

describes a simple method of making aliphatic nitriles from no more than heating the ammonium salt of the corresponding acid plus some excess free acid.

So, for example acetonitrile, requires amonium acetate, plus an excess of acetic acid (about 40-60% compared to how much acetate you use).  This is then heated to around 200-220*C for a time and then the acetonitrile can be purified simply by first salting out the nitrile with acetate salt and then fractionally distilling.

Apparently, use of a catlayst speeds thing up immensly, and, as a bonus, the catalyst is simply an iron compound - the one they name is Fe(H2PO4)3, or they say just use a corrosion-resistant iron vessel, which will corrode slightly to provide enough catalyst!!

They provide an example of running this as a continuous flow process:
A mixture of about 88% ammonium acetate and 12% acetic acid, prepared by adding acetic acid to ammonium carbonate, is continuously fed to a still prvided with a vigruex column and containing either a quantity of the feed mixture or a residue from a previous operation.  During the process the base is maintained at a temperature of 203-209*C and the head at 90-95*C.  (They then go and purify it - the point of keeping the head at 95* is to allow the nitrile formed to continuously distil over, while the acid etc. is returned to the flask.  Also, note they used less acid than I mentioned above - apparently when running this as a flow process the acid quantity can be reduced).