. Methods of Preparation of carboxylic acids Some important methods for the preparation of carboxylic acids are as follows : . From Primary alcohols and aldehydes Primary alcohols and aldehydes can easily be oxidised to the corresponding carboxylic acids with oxidising agents such as potassium permanganate (in acidic or alkaline medium), potassium dichromate (in acidic medium) Example (O) H + / K Cr O (O) Ethyl alcohol Acetaldehyde Acetic acid CH CH OH CH CHO CH COOH . Hydrolysis of Nitriles Nitriles yield carboxylic acids when subjected to hydrolysis with an acid or alkali.
Example N + 2H O CH COOH + NH H + Methyl cyanide Acetic acid . Acidic hydrolysis of esters Esters on hydrolysis with dilute mineral acids yield corresponding carboxylic acid Example OC H + H O H + Ethyl acetate Acetic acid OH + C H OH Ethyl alcohol . From Grignard reagent Grignard reagent reacts with carbon di oxide (dry ice) to form salts of carboxylic acid which in turn give corresponding carboxylic acid after acidification with mineral acid. Example O + CH MgBr dry ether H O H + OMgBr OH + Mg Br Methyl Magnessium bromide Acetic acid O + dry ether H O H + OMgBr OH + Mg X Benzoic acid MgBr Phenyl Magnesium Bromide XII U12-Carbonyl XII U12-Carbonyl - - - - Formic acid cannot be prepared by Grignard reagent since the acid contains only one carbon atom .
Hydrolysis of acylhalides and anhydrides a) Acid chlorides when hydrolysed with water give Carboxylic acids. Example Cl + H O Acetyl chloride OH + HCl Acetic acid b) Acid anhydride when hydrolysed with water give corresponding carboxylic acids. CH + H O 2CH C OH Acetic anhydride Acetic Acid C H Benzoic anhydride 2C H Benzoic acid C H + H O . Oxidation of alkyl benzenes Aromatic carboxylic acids can be prepared by vigorous oxidation