The tertiary bromide shown (one diastereomer, single enantiomer) is hydrolysed in water-acetone by a pure S_N1 pathway. Which description of the tertiary alcohol product is correct?

Two diastereomers, each optically active, in unequal amounts

One diastereomer only, optically active

A racemic mixture of one diastereomer, optically inactive

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JEE Main levelSingle correct optionDifficulty 2 of 3o3240

The tertiary bromide shown (one diastereomer, single enantiomer) is hydrolysed in water-acetone by a pure $S X_{N} 1$ pathway. Which description of the tertiary alcohol product is correct?

ATwo diastereomers, each optically active, in unequal amounts
BOne diastereomer only, optically active
CA racemic mixture of one diastereomer, optically inactive
DA single meso compound

Answer: A

The compound is 1-bromo-1,3-dimethylcyclohexane (one stereoisomer drawn). Water attacks the planar cation from either face, creating the cis and trans alcohols (1,3-dimethylcyclohexan-1-ol), but the C3 stereocentre is untouched and the two are diastereomers, so they form in unequal amounts. Each is chiral (neither is meso; RDKit gives 4 stereoisomers of the constitution, none meso), so both products are optically active.

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The tertiary bromide shown (one diastereomer, single enantiomer) is hydrolysed in water-acetone by a pure SXN​1 pathway. Which description of the tertiary alcohol product is correct?

Answer: A

More questions on Stereochemical outcome of substitution on drawn chiral substrates

The tertiary bromide shown (one diastereomer, single enantiomer) is hydrolysed in water-acetone by a pure $S X_{N} 1$ pathway. Which description of the tertiary alcohol product is correct?