Identify A in the given chemical reaction.

Step 1: Identify the reaction type

The reaction involves $\ce{Mo2O3}$ (or similar aromatization catalyst) acting on a cyclic hydrocarbon. $\ce{Mo2O3}$ is an aromatization reagent that converts cyclohexane derivatives to aromatic compounds by dehydrogenation.

Step 2: Trace the reaction

The reaction sequence converts compound A (an aromatic compound) back from its precursor:

• $\ce{Mo2O3}$ promotes aromatization: cyclohexane → benzene, methylcyclohexane → toluene
• The reaction involves oxidative dehydrogenation

Step 3: Identify A

Given that the product involves the aromatic ring with a methyl substituent, compound A = Toluene ($\ce{C6H5CH3}$).

The reaction is: methylcyclohexane $\xrightarrow{\ce{Mo2O3}}$ toluene + $\ce{3H2}$

Working backwards: A (toluene) is the aromatic product.

Answer: Option (a) — Toluene

Key Points to Remember:

• $\ce{Mo2O3}$ is an aromatization catalyst (dehydrogenation)
• Cyclohexane → Benzene (aromatization): loses 3 $\ce{H2}$
• Methylcyclohexane → Toluene: loses 3 $\ce{H2}$
• This reaction is important in catalytic reforming of petroleum