The secondary bromide shown is solvolysed in warm ethanol and gives a tertiary ether as a major product. Which carbocation is formed from the first-formed secondary cation by a single 1,2-shift?

AThe tertiary 2-methylbut-2-yl cation, formed by a 1,2-hydride shift
BA primary cation, formed by a methyl shift
CA secondary cation that stays unchanged
DA carbanion, formed by loss of Br+

Answer: A

The compound is 2-bromo-3-methylbutane. Ionisation gives a secondary cation next to a carbon bearing one hydrogen and two methyls. A 1,2-hydride shift moves the cation to that carbon, giving the tertiary 2-methylbut-2-yl cation, which is trapped by ethanol to give 2-ethoxy-2-methylbutane.

Practice Organic Reaction Mechanisms III: Nucleophilic Substitution More on SN1 rearrangement and neighbouring group participation in drawn substrates

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The secondary bromide shown is solvolysed in warm ethanol and gives a tertiary ether as a major product. Which carbocation is formed from the first-formed secondary cation by a single 1,2-shift?

Answer: A

More questions on SN1 rearrangement and neighbouring group participation in drawn substrates