Identify the major products A and B respectively in the following set of reactions.

Solution

Chemistry ma’am · 4 steps

Acid and heat remove water to give the more substituted alkene; acetyl chloride turns the OH into an ester.

1. Carbocation first. The starting alcohol is 1-methylcyclohexan-1-ol, a tertiary alcohol. Conc. H₂SO₄ protonates the OH, water leaves, and a stable tertiary carbocation forms at C-1.
2. Which H is lost. A proton can leave from a ring carbon next to C-1 or from the methyl group. By Saytzeff's rule, the more substituted alkene is the major product.

   H removed from	Alkene formed	Alkyl groups on C=C	Result
   ring CH₂ (C-2)	1-methylcyclohexene (C=C inside the ring)	3, trisubstituted	major, this is A
   CH₃ group	methylenecyclohexane (C=C outside the ring)	2, disubstituted	minor

3. Acetylation. With CH₃COCl and pyridine, the O of the OH group attacks the acyl chloride, and pyridine takes up the HCl formed. The H of OH is replaced by COCH₃, so B is the ester 1-methylcyclohexyl acetate. No ring carbon is touched.
4. So. A is 1-methylcyclohexene and B is 1-methylcyclohexyl acetate, which is option (b).

The idea to keep. Acid-catalysed dehydration goes through a carbocation and gives the most substituted alkene. Acyl chloride with pyridine acylates the oxygen of an alcohol, never a carbon of a saturated ring.

Answer from the NTA final answer key. Solution by PrepWiser.