Formation of carboxylate anions

Reduction of carboxylic acids to primary alcohol
(Lithium aluminum hydride is the only effective reagent for reducing acids to   primary alcohols)

Alpha bromination of alkanoic acids
(the final product is a-bromo carboxylic acid

Decarboxylation of B-keto acids to form ketones

Decarboxylation makes the malonic acid lose a carbon dioxide group

Carboxylation of organometallics
(Alkyl and aryl bromides are converted into Grignard reagents which add to the carbonyl group of carbon dioxide. Adding acid then makes the acid group.

Getting carboxylic acids from nitriles

Getting carboxylic acids from nitriles