2-Bromo-2-methylpropane is hydrolysed in 80% aqueous ethanol. Which statements are correct?

AThe rate is independent of the concentration of any added $OH X^{-}$ .
BThe mechanism is a single concerted step with backside attack.
CA carbocation is formed in the rate-determining step.
DIncreasing the water content of the solvent increases the rate.

Answer: A, C, D

A tertiary halide reacts by

S_{N} 1

: slow ionisation to

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

then fast capture by solvent, so rate

= k [halide]

and the nucleophile concentration does not matter. A more polar, more ionising solvent (more water) stabilises the ionic transition state and speeds up ionisation. The concerted backside-attack description belongs to

S_{N} 2

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2-Bromo-2-methylpropane is hydrolysed in 80% aqueous ethanol. Which statements are correct?

Answer: A, C, D

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