One or more options correct
Considering regiochemistry, stereochemistry and rearrangements in the reactions of alkenes, phenol and acetophenone, choose the correct statement(s).
- A. Hydroboration–oxidation of 1-methylcyclohexene gives, as the major product, racemic trans-2-methylcyclohexan-1-ol
- B. Acid-catalysed hydration of 3,3-dimethylbut-1-ene gives 3,3-dimethylbutan-2-ol as the major product
- C. The Reimer–Tiemann reaction of phenol with and aqueous NaOH gives mainly 4-hydroxybenzaldehyde
- D. Acetophenone on treatment with followed by acidification gives iodoform and phenylacetic acid
Show answer and solution
Answer: A
A: Boron adds to the less hindered, less substituted alkene carbon and H and B add syn from the less hindered face; oxidation retains configuration, so H and OH end up cis and the methyl and OH are trans: racemic trans-2-methylcyclohexanol. Correct. B: the secondary carbocation formed from 3,3-dimethylbut-1-ene undergoes a methyl shift to the tertiary cation, so the major product is 2,3-dimethylbutan-2-ol; incorrect. C: ortho attack by dichlorocarbene on the phenoxide (Na chelation) dominates, giving mainly salicylaldehyde; incorrect. D: the haloform reaction removes the methyl, converting to , i.e. benzoic acid (not phenylacetic acid) and ; incorrect. Only A is correct.
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