Amide from a Carboxylic Acid in One Step?

[roycer]

I just had a question:

Can you prepare amides from carboxylic acids from the reaction of a carboxylic acid and ammonia? In Kaplan's chapter on Carboxylic Acid Derivatives, it is shown that this reaction actually produces an ammonium salt of a carboxylate anion. But, in one of their end-of-chapter problems, they say that this reaction actually does produce the amide.

Anybody?

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[bigman225]

It produces the ammonium salt. Comparing the relative acidities/basicities, and the fact that carboxylic acids' carbonyl carbon isn't very electrophillic. The carboxylate anions are extremely stable (the negative charge is delocalized onto both electrons, which is why they have fairly low pKas), also.

I'm pretty sure you prepare amides from carboxylic acids using SOCL2, PBR3, or some other halogenating reagent and then with the appropriate amine.


edit: confirmed by textbook

 

[roycer]

I'm pretty sure it produces the ammonium salt. Comparing the relative acidities/basicities, and the fact that carboxylic acids' carbonyl carbon isn't very electrophillic. I'm pretty sure you prepare amides from carboxylic acids using SOCL2, or some other halogenating reagent and then treatening with the appropriate amine.

Yes, the reaction using SOCl2 and then ammonia is a good way to produce the amide. I thought it was weird Kaplan would say reaction of ammonia with a carboxylic acid would produce the amide.

 

[bigman225]

Yeah, that must be a typo...

 

[ocwaveoc]

Don't quote me on this but I think there is a way if you add something called DCC. So, an ammonia + carboxylic acid in DCC would give an amide in one step. However, this is not a preferred method. I don't have my text book with me so I can't double check this. I thought it was a strange reaction since you'd not expect this to happen.

 

[rhizotummy]

I just had a question:

Can you prepare amides from carboxylic acids from the reaction of a carboxylic acid and ammonia? In Kaplan's chapter on Carboxylic Acid Derivatives, it is shown that this reaction actually produces an ammonium salt of a carboxylate anion. But, in one of their end-of-chapter problems, they say that this reaction actually does produce the amide.

Anybody?

I think you might be able to make an amide from ammonia and a deprotonated carboxyllic acid. However, mixing a protonated carboxyllic acid with ammonia won't produce an amide b/c the amide will get protonated from the carboxyllic acid and will be a horrible nucleophile.

Summary: you can make amides from carboxyllic acids + ammonia in basic conditions?

...atleast I think lol

 

[Psychotropic]

I think you might be able to make an amide from ammonia and a deprotonated carboxyllic acid. However, mixing a protonated carboxyllic acid with ammonia won't produce an amide b/c the amide will get protonated from the carboxyllic acid and will be a horrible nucleophile.

Summary: you can make amides from carboxyllic acids + ammonia in basic conditions?

...atleast I think lol

It would be tough to make an amide from a CA and ammonia in a basic solution (think about the leaving group in the addition elimination reaction). It is possible to make an amide from a CA and ammonia if you cook the solution for some time. The acid base reaction is kinetically favorable, however, given the right amount of heat and time you can make an amide (though your yield rate will suck).