Question

Which of the following is produced when $R - OH$ reacts with $PC{l_3}$ ?
(A) $R - Cl$
(B) $R - H$
(C) $HCl$
(D) ${H_2}O$

Answer 1

Alcohols are the chemical compounds that consist of the $- OH$ group. When alcohols react with compounds like phosphorous trichloride, the $- OH$ group in alcohols can be replaced by $Br$ atoms. This mechanism is known as a bimolecular nucleophilic substitution reaction.

Complete Step By Step Answer:
Chemical compounds are classified into functional groups based on the groups present in them. Alcohols are one of the important functional groups consisting of a $- OH$ group.
Phosphorus trichloride is an inorganic compound and has the molecular formula of $PC{l_3}$
When alcohols react with $PC{l_3}$ alkyl halides will be formed.
The replacement of one group by another group is known as a substitution reaction. There are two types of substitution reactions namely nucleophilic substitution and electrophilic substitution reaction. In nucleophilic substitution reaction also, they were two different types namely unimolecular nucleophilic substitution reaction $\left( {S{N^1}} \right)$ and bimolecular nucleophilic substitution reaction $\left( {S{N^2}} \right)$ .
Given a molecule is $R - OH$ it consists of a hydroxyl group, when this compound is treated with $PC{l_3}$ , the $- OH$ group can be replaced by $Br$ . As $R$ represents an aliphatic alcohol, this compound undergoes bimolecular nucleophilic substitution reaction $\left( {S{N^2}} \right)$ .
Thus, the product will be $R - Cl$ which is an alkyl halide and is known as alkyl chloride.
$R - Cl$ is produced when $R - OH$ reacts with $PC{l_3}$.
Option A is the correct one.

Note:
Primary alcohols do not have a steric effect and undergo a bimolecular nucleophilic substitution reaction, where the intermediate is a transition state. Tertiary alcohols undergo unimolecular substitution reaction, where the intermediate is tertiary carbocation which is a stable one.