2-Bromo-3-methylpentane (any mixture of its stereoisomers) is solvolysed in methanol. Consider only substitution products (methyl ethers) arising either from the original secondary cation or from the cation reached from it by a single 1,2-hydride shift to a tertiary centre; ignore elimination and further shifts. Counting every stereoisomer separately, how many different ethers can form? Give the answer as an integer.

Numerical answer type, tolerance 0.5.

Answer: 5

The secondary cation

CH X_{3} - CH X^{+} - CH (CH X_{3}) - CH X_{2} CH X_{3}

is trapped by methanol to give 2-methoxy-3-methylpentane, which has two stereocentres (C-2, C-3): 4 stereoisomers. A hydride shift from C-3 gives the tertiary cation

CH X_{3} CH X_{2} - C X^{+} (CH X_{3}) - CH X_{2} CH X_{3}

, which gives 3-methoxy-3-methylpentane, with no stereocentre: 1 compound. Total

4 + 1 = 5

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Answer: 5

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