Zock4 - 14-6-2016 at 04:45
Hello,
Im from Germany so sorry for the, not mother tung like, English.
I've read that carboxylic acid amides can be prepared using their esters and concentrated ammonia/ammonium hydroxide solution.
Unfortunately I've also read that benzamide can't be prepared that way.
Is it true or is it possible to make benzamide from n-propyl benzoate and 25 percent ammonia solution ? Also I wonder whether it is necessary to
distill the ester before use or if I can clean it enough with dilute sodium hydrogen carbonate solution, saturated sodium chloride solution and a
drying agent like anhydrous magnesium sulfate, etc. I don't really want do ditill it because it has a compareably high boiling point and I don't want
to crack my glassware.
Also how much time do you recommend for refluxing the benzoic acid with the n-propanole and how much concentrated sulfuric acid is required ?
Greetings from Germany.
notoxicshit - 14-6-2016 at 05:03
A lengthy discussion on benzamide production from benzoic acid and nurea can be found here. Garage chemist for example did several successful
experiments amongst others.
Both materials are OTC available and cheap as shit.
Dr.Bob - 14-6-2016 at 05:33
Making the amide from ester and ammonia can work in many cases, not sure if benamides work that way or not, best way to find out if an experiment.
Of course, in water, hydrolysis to the benzoic acid is also likely. Using a non-aqueous solvent is far better, if you can dissolve in dioxane or THF
and then bubble ammonia through is far better, even ammonia in iso-propanol would work.
Purification of the ester is not needed. You will need to run the reaction and see check by TLC or other means, hard to predict the rate of a
reaction without knowing all conditions. You will also likely need to keep adding small amounts of ammonia, as it will boil off over time. Not
sure what you need sulfuric for, other than maybe workup, but might need need any then, as ammonia will evaporate. But the urea and acid may be
better route.