Question

Identify the product of reforming reaction of n-hexane in the presence of \(\text{V}_2\text{O}_5\) over alumina.

• A. Benzene
• B. Cyclohexane
• C. Methyl benzene
• D. Phenol

Hint:

Reforming of n-hexane over a metal oxide catalyst gives an aromatic ring.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Reforming (aromatisation) converts straight-chain alkanes with six or more carbons into aromatic hydrocarbons. It uses a catalyst such as \(V_2O_5\), \(Mo_2O_3\) or \(Cr_2O_3\) on alumina at high temperature and pressure.

Step 2: Reaction:
n-Hexane loses hydrogen, closes into a ring, and loses more hydrogen to give a fully conjugated six-membered ring:
\[ CH_3(CH_2)_4CH_3 \xrightarrow{V_2O_5/Al_2O_3,\ \Delta} C_6H_6 + 4H_2 \]

Step 3: Check the options:
Cyclohexane is only the ring without full dehydrogenation. Methylbenzene needs a seventh carbon, so n-heptane would be needed. Phenol contains oxygen, which is absent from the reactant. So the product is benzene, option (A).

Final Answer:
Aromatisation of n-hexane gives benzene. \[ \boxed{A:\ \text{Benzene}} \]