Pick the alkyl halide in the pair that reacts with sodium iodide in acetone at the faster rate. Select the single best answer. 1−Chlorohexane or Cyclohexyl chloride 1−Chlorohexane reacts at the faster rate. Cyclohexyl chloride reacts at the faster rate.

1-chlorohexane is faster

Explanation:

In this case, all we need to do is to know the function of the reagent in the reaction, in other words, we need to know if the reagent promoves a Sn1 or Sn2 reaction.

If the reagent promoves a Sn1 reaction, the faster rate will be the reactant with the most stable carbon, which follows the order 3° > 2° >> 1°.

If the reagent promoves a Sn2 reaction, the faster rate will be the reactant with the less stable carbon, in the order 1° > 2° >> 3°.

This is because, the Sn2 reaction is a bimolecular reaction that it's really fast and use only 1 step. It actually doesn't leave carbocations intermediate, that's why it's neccesary that the reactant has the less stability and least steric hindrance.

Taking this into account, the NaI in acetone is a reagent that always promoves either a Sn2 reaction or E2. As it's promoving the Sn2 reaction, let's see which is more stable between chlorohexane and cyclohexylchloride.

The chlorine in the cyclohexyl, it's on a secondary carbon ( CH2 - CH - Cl), while the chlorine in the chlorohexane it's on a primary carbon (CH2 - Cl); also the chlorohexane do not have steric hindrance, while the cyclohexyl has a little because of the cyclo, making the Sn2 reaction slower.

Therefore, the Chlorohexane would have the faster rate