Question

In substitution reactions, (CH3)3C-I reacts at the same rate with Br- and Cl- even though Br- is a more reactive nucleophile than Cl-. Why?A. (CH3)3C-Br reacts by SN1 mechanism whose rate is independent of nucleophile reactivity. B. (CH3)3C-Br reacts by SN2 mechanism and therefore all nucleophiles react at the same rate regardless of their reactivity. C. The t-butyl carbocation is so reactive, the measurable rate of it's reaction with different nucleophiles is imperceptible. D. The t-butyl group sterically hinders nucleophiles, making different nucleophiles appear to react at the same rate.

Answer 1

Answer:

A. (CH3)3C-I reacts by SN1 mechanism whose rate is independent of nucleophile reactivity.

Explanation:

We must recall that (CH3)3C-I is a tertiary alkyl halide. Tertiary alkyl halides preferentially undergo substitution reaction via SN1 mechanism.

In SN1 mechanism, the rate of reaction depends solely on the concentration of the alkyl halide (unimolecular mechanism) and is independent of the concentration of the nucleophile. As a result of this, both Br^- and Cl^- react at the same rate.