The cyclic diol shown is heated with dilute H2SO4. Which structure is the main product (a ring-expansion pinacol rearrangement)?

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JEE Main levelSingle correct optionDifficulty 2 of 3ap225

The cyclic diol shown is heated with dilute $H X_{2} SO X_{4}$ . Which structure is the main product (a ring-expansion pinacol rearrangement)?

AStructure A
BStructure B
CStructure C
DStructure D

Answer: C

The diol is 1,1'-bi(cyclohexyl)-1,1'-diol. After loss of water from one ring, a ring

CH X_{2}

of the other ring migrates to the cation, which enlarges that ring to seven members and leaves the carbonyl next to the new spiro carbon. The product is spiro[5.6]dodecan-7-one, with the ketone in the seven-membered ring.

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Answer: C

More questions on Pinacol rearrangement products of drawn diols

The cyclic diol shown is heated with dilute $H X_{2} SO X_{4}$ . Which structure is the main product (a ring-expansion pinacol rearrangement)?