The compound which does not lead to benzoic acid by oxidation with KMnO4 is t -butylbenzene. In this compound, the side chain has no C−H bond at α -carbon (with respect to benzene nucleus) Hence, benzene ring get cleaved.
Toluene, benzyl alcohol, n -butyl benzene and styrene all contain one benzylic C −H bond and on oxidation forms benzoic acid.