The compound shown is heated with hot alkaline $\mathrm{KMnO}{}_4$ and the mixture is then acidified. Which structure is the organic product?

The compound shown is toluene. Hot alkaline permanganate oxidises any alkyl side chain with a benzylic hydrogen completely to $-\mathrm{COOH}$, so the methyl group becomes the carboxylic acid group. The product is benzoic acid, not the aldehyde or the alcohol, which are intermediates.