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Why does mixing a carboxylic acid with ammonia usually form a salt rather than an amide?

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oxidation of alcohols — carboxylic acid Alcohols may be oxidized to give aldehydes, ketones, and carboxylic acids. The oxidation of organic compounds generally increases the number of bonds from carbon to oxygen, and it may decrease the number of bonds to hydrogen.

When a carboxylic acid is mixed with ammonia, the reaction does not produce an amide because the carboxylic acid is not susceptible to nucleophilic attack at the carbonyl group under these conditions.12

Instead, the ammonia acts as a base rather than a nucleophile. It readily removes a hydrogen ion ( $H^{+}$ ) from the acidic carboxyl group, which results in the formation of a salt ( $R C O O^{-} N H_{4}^{+}$ ).12

Because carboxylic acids do not undergo the necessary nucleophilic substitution directly with ammonia, the synthesis of amides typically requires more reactive intermediates, such as acyl chlorides or anhydrides, or the use of specific coupling reagents like dicyclohexylcarbodiimide (DCC).13