The ketone shown is treated with methylmagnesium bromide and then aqueous acid. The product is then heated with concentrated sulphuric acid. Which structure is the major final organic product?

AStructure A
BStructure B
CStructure C
DStructure D

Answer: B

Cyclohexanone adds the methyl group to give 1-methylcyclohexan-1-ol. Acid-catalysed dehydration of this tertiary alcohol proceeds by E1 through the tertiary cation and follows Zaitsev's rule, giving the more substituted endocyclic alkene 1-methylcyclohexene.

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