Cyclohexanol undergoes a series of reactions as given. Identify compound (iv). C ₆ H ₁₁ OH + CrO ₃ ( i )+ C ₆ H ₅ MgI ( ii )+ dil. HCl ( iii )+ Conc. H ₃ PO ₄ ( iv )

Step-by-step solution

C₆H₁₁OH + CrO₃ Cyclohexanone (i) — CrO₃ oxidises secondary alcohol to ketone. 3: Cyclohexanone + C₆H₅MgI then dil. HCl — Grignard reagent adds phenyl group to carbonyl carbon, followed by protonation to give 1-phenylcyclohexanol (iii) — a tertiary alcohol. 1-phenylcyclohexanol + Conc. H₃PO₄ dehydration (E1), loss of H₂O gives 1-phenylcyclohexene (iv) — double bond forms in conjugation with phenyl ring for maximum stability. Compound (iv) is 1-phenylcyclohexene — option (4).