morsagh - 16-11-2015 at 04:44
Can be benzamide prepared by heating ammonium salt of benzoic acid? Are there any problems with this synthesis?
gdflp - 16-11-2015 at 07:06
A much better, or at least more well documented, synthesis entails heating benzoic acid with urea and boric acid at 180°C for 2.5 hours. See here. In practice, I have found that undershooting this temperature slightly is much better than overshooting it and the yield suffers if the
melt is heated beyond 185°C for any significant period of time.
Praxichys - 16-11-2015 at 07:31
Gah, that reflux/heat procedure is a PITA every time. A much better way is the ammonolysis of a benzoate ester.
Make methyl benzoate from the benzoic acid, then just mix it with concentrated aqueous ammonia and let it sit for a week. The ammonia base-catalyzes
ester breakage, leaving the acid amide and the alcohol. Works great and the yields are typically high with this method. When I needed acetamide I did
this with ethyl acetate.
After the week is up, just boil out the water/alcohol/leftover benzoate and you're left with benzamide, which you can either recrystallize or distill
under vacuum.
[Edited on 16-11-2015 by Praxichys]
morsagh - 20-11-2015 at 11:53
So, i have tried heating of ammonium benzoate, for about 5 minutes of heating and at one point it melted, so i cooled it down and put in NaOH solution
and most of melted material didn´t dissolved, just after heating and with typical smell of ammonia. I think that somebody with serious equipment for
heating should try it.