Question

Identify the type of substitution ${\mathbf{SN}}_{\mathbf{1}}\mathbf{,}{\mathbf{SN}}_{\mathbf{2}}$mechanism involved in the conversion of the alcohol shown into the corresponding alkyl halide.

(a)

(b)

(c)

Short answer

(a)

(b)

Step-by-step solution

Step 1: Reaction of alcohol with an alkyl halide

The reaction of alcohol with alkyl halide follows the${\mathbf{SN}}_{\mathbf{1}}$ mechanism.

It’s a reaction that leads to removal of the hydroxyl group followed by loss of water and formation of carbocation occur and the addition of the halide act as nucleophile occurs as follows:

Formation of alkyl halide

Step 2: Reaction of alcohol with  PBr3

The reaction of alcohol with alkyl halide follows the ${\mathbf{SN}}_{\mathbf{2}}$ mechanism

It’s a reaction that leads to removal of the hydroxyl group followed by loss of water and addition of the halide act as nucleophile occur simultaneously without intermediate formation as follows:

Formation of Alkyl halide

Step 3: Reaction of alcohol with tosylate

The reaction of alcohol with alkyl halide follows the${\mathbf{SN}}_{\mathbf{2}}$ mechanism.

It’s a reaction that leads to removal of the hydroxyl group followed by loss of water and addition of the tosylate occur which act as nucleophile occur simultaneously without the intermediate formation and then on addition with sodium bromide tosylate leave because tosylate is the best leaving group and addition of Br ion occurs as follow:

Formation of Alkyl halide