Question

n-Butanol (CH3CH2CH2CH2OH) and t-butanol ((CH3)3COH) are converted to their corresponding alkyl chorides on being reacted with hydrogen chloride. Write out an equation for each reaction Assign each the appropriate symbol (SN1 or SN2) Write a suitable mechanism for each reaction.

Answer 1

Answer: n-Butanol are converted using SN2 and tert-butanol is converted using SN1

Explanation: For the conversion of n-butanol into butyl chloride using Hydrogen Chloride the reaction would follow SN2 mechanism.

SN2 reaction mechanism occurs only in the case of primary substrates as it is a one step mechanism that happens in a concerted manner. It involves backside attack of nucleophile on the substrate such that the nucleophile attacks from the back side and leaving group leaves from the front side.

In this reaction since hydroxy group (OH) is not a good leaving group hence firstly we need to convert it into a good leaving group. When we treat n-butanol with HCl hydroxy group is protonated and now it turns into a good leaving group as it can leave as H₂O.

Cl⁻ here acts as nucleophile and now attacks the primary carbon center from the back side which contains the protonated hydroxy group as a leaving group.

In the case of tertiary butanol the reaction follows SN1 mechanism and it is 2 step mechanism.

In the first step hydroxy group is protonated and as it becomes a good leaving group it leaves and leads to the formation of a stable tertiary carbocation as an intermediate.

In the second step this intermediate carbocation is attacked by the Cl⁻ nucleophile which leads to the formation of tertiary butyl chloride.

Kindly find in attachment the reaction mechanism for both the reactions.