Q 31 E - Organic Chemistry (Mcmurry)

Question

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

a. 

b) 

c) 

Step-by-Step Solution

Answer

a) 

b) 

c) 

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 the removal of the hydroxyl group, followed by the loss of water. The formation of carbocation occurs, and the addition of the halide acts as the nucleophile , as follows:

Step 2 : Reaction of alcohol with PBr 3

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

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

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 the removal of the hydroxyl group, followed by the loss of water. The addition of the tosylate occurs, which acts as the nucleophile occur simultaneously without the intermediate formation. When added to sodium bromide, the tosylate leaves because tosylate is the best leaving group, and the addition of Br ion occurs as follows: