Phenyl methyl ketone is Acetophenone ($C_6H_5COCH_3$). The conversion of acetophenone to ethylbenzene ($C_6H_5CH_2CH_3$) involves the reduction of the carbonyl group ($>C=O$) to a methylene group ($-CH_2-$). This specific transformation is achieved using Zinc amalgam and concentrated hydrochloric acid (Zn-Hg + HCl), a reaction known as the Clemmensen Reduction.

$LiAlH_4$ is a reducing agent that would reduce the ketone to a secondary alcohol (1-phenylethanol), not a hydrocarbon. $KMnO_4$ is a strong oxidizing agent and would not reduce the carbonyl group.

• Zn-Hg/HCl is the standard reagent for reducing aldehydes and ketones to alkanes in acidic media.