Question

Addition of $KI$ accelerates the hydrolysis of primary alkyl halides because:
(A) $KI$ is soluble in organic solvents
(B) The iodide ion is a weak base and a poor leaving group
(C) The iodide ion is a strong base
(D) The iodide ion is a powerful nucleophile as well as a good leaving group

Answer 1

$KI$performs an attack on the carbon atom of alkyl halide and helps to eject the nucleophile. Wherein the iodide ion attacks the alkyl halide to form alkyl halide by $S{{N}_{2}}$mechanism.

Complete step by step answer:
- Potassium iodide, $KI$is a strong reducing agent. It is a colourless reagent which itself gets oxidised in the process of reducing another substance.
- Since alkyl halides on alkaline hydrolysis form alcohols. In$KI$, iodide ion being larger in size, has greater polarising ability. Due to which it tends to replace other halogen from alkyl halide to form a new bondage an intermediate.
- The latter hydroxide ions come to attack on the site. In the case of normal alkyl group reaction follows SN2. Iodide ion gets replaced easily, as it is a better leaving group. Hence hydrolysis is facilitated.

The answer to the above question is (D) The iodide ion is a powerful nucleophile as well as a good leaving group

Additional information: It is widely used in laboratories because it is hygroscopic than sodium iodide which in turn makes it easier to work with $KI$. It is also used in the preparation of silver iodide for high speed photographic film.

Note: Iodide ion attacks the alkyl halide to form alkyl iodide by $S{{N}_{2}}$ mechanism, after that hydrolysis go through by $S{{N}_{1}}$mechanism due to iodide being a better leaving group.