Preparation of Carboxylic acids:
The compound in which the carbonyl group is attached to hydroxyl then it is called Carboxylic acid. There are various methods that can be used for the preparation of Carboxylic acids.
By using primary alcohols and aldehyde:
We will notice that the primary alcohol gets oxidised to carboxylic acid when oxidising agents are added such as potassium permanganate (KMnO4) in an acidic, alkaline or neutral medium. On using mild oxidising agent we can get carboxylic acids from aldehydes.
We can get aromatic carboxylic acids after vigorous oxidation of alkyl benzenes with chromic acid. Irrespective of the length of the chain the whole side chain is oxidised to a carbonyl group. The oxidation of primary and secondary alkyl groups can be done in this manner while the tertiary group is unaffected.
From nitriles and amides:
Amides are prepared by the hydrolysis of nitriles and then is converted to acids in the presence of catalysts (H+ or OH-1). In order to stop the reaction at amide stage, mild reaction conditions are used.
By using Grignard reagents:
When Grignard reagent reacts with carbon dioxide its forms salts of carboxylic acids which after some time gives corresponding carboxylic acid after the acidification with any mineral acid. We can prepare Grignard reagents as well as nitriles from alkyl halides. These methods are very useful for the conversion of alkyl halides into corresponding carboxylic acids which has one carbon atom more than what is present in alkyl halides.
By acyl halides and anhydrides:
When acid chloride is hydrolyzed with water then carboxylic acid is produced and it is more readily hydrolyzed with aqueous base and gives corresponding carboxylic ions which on further acidification gives the carboxylic acid.
By using esters:
A carboxylic acid is produced after the acidic hydrolysis of esters and carboxylates are produced after the basic hydrolysis of an ester.