Show how each of the following compounds can be converted to benzoic acid.
$(i)$ Ethylbenzene
$(ii)$ Acetophenone
$(iii)$ Bromobenzene
$(iv)$ Phenylethene (Styrene)

(N/A) The conversion of the given compounds to benzoic acid is as follows:
$(i)$ Ethylbenzene: Oxidation with alkaline $KMnO_4$ followed by acidification gives benzoic acid.
$C_6H_5CH_2CH_3$ $\xrightarrow{KMnO_4/KOH, \Delta} C_6H_5COOK$ $\xrightarrow{H_3O^+} C_6H_5COOH$
$(ii)$ Acetophenone: Oxidation with alkaline $KMnO_4$ followed by acidification gives benzoic acid.
$C_6H_5COCH_3$ $\xrightarrow{KMnO_4/KOH, \Delta} C_6H_5COOK$ $\xrightarrow{H_3O^+} C_6H_5COOH$
$(iii)$ Bromobenzene: Reacts with $Mg$ in dry ether to form phenylmagnesium bromide,which reacts with $CO_2$ (dry ice) followed by acidification to give benzoic acid.
$C_6H_5Br$ $\xrightarrow{Mg, \text{ether}} C_6H_5MgBr$ $\xrightarrow{CO_2} C_6H_5COOMgBr$ $\xrightarrow{H_3O^+} C_6H_5COOH$
$(iv)$ Phenylethene (Styrene): Oxidation with alkaline $KMnO_4$ followed by acidification gives benzoic acid.
$C_6H_5CH=CH_2$ $\xrightarrow{KMnO_4/KOH, \Delta} C_6H_5COOK$ $\xrightarrow{H_3O^+} C_6H_5COOH$