Aromatic carboxylic acids are prepared by oxidizing alkylbenzenes using chromic acid or acidic/alkaline potassium permanganate. The entire side chain is oxidized to the carboxyl group, with primary and secondary alkyl groups affected while tertiary groups remain unaffected.
How are aromatic carboxylic acids synthesized from alkylbenzenes, and what happens to the entire side chain during the oxidation process?
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Aromatic carboxylic acids are synthesized from alkylbenzenes through a process known as side-chain oxidation. The alkylbenzene undergoes oxidation using strong oxidizing agents like chromates or permanganates, resulting in the removal of the entire alkyl side chain. This reaction converts the alkylbenzene into the corresponding aromatic carboxylic acid. For example, toluene (methylbenzene) is oxidized to benzoic acid. The side-chain oxidation involves breaking the carbon-carbon bonds in the alkyl group, leaving only the aromatic ring, which is then functionalized with a carboxyl group. This method is essential in the synthesis of aromatic carboxylic acids from hydrocarbons.