Question

The reaction of propene with ${\text{HOCl }}\left( {{\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}} \right)$ proceeds through the intermediate:
A.${\text{C}}{{\text{H}}_3} - {\text{C}}{{\text{H}}^ + } - {\text{C}}{{\text{H}}_2} - {\text{Cl}}$
B.${\text{C}}{{\text{H}}_3} - {\text{CH}}\left( {{\text{OH}}} \right) - {\text{CH}}_2^ +$
C.${\text{C}}{{\text{H}}_3} - {\text{CH}}\left( {{\text{Cl}}} \right) - {\text{CH}}_2^ +$
D.${\text{C}}{{\text{H}}_3} - {\text{C}}{{\text{H}}^ + } - {\text{C}}{{\text{H}}_2} - {\text{OH}}$

Answer 1

The formation of carbocation provides the intermediate stage which can be observed when positively charged chlorine atom attacks on propene.The reaction of propene with ${\text{HOCl}}$ in the presence of ${\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$ is an addition reaction. ${\text{HOCl}}$ contains ${\text{O}}{{\text{H}}^ - }$ and ${\text{C}}{{\text{l}}^ + }$.

Step by step answer: The structure of propene is ${\text{C}}{{\text{H}}_{\text{3}}} - {\text{CH}} = {\text{C}}{{\text{H}}_{\text{2}}}$. Propene reacts with ${\text{HOCl}}$ as follows:

The ${\text{HOCl}}$ contains ${\text{O}}{{\text{H}}^ - }$ and ${\text{C}}{{\text{l}}^ + }$.
In the first step of the reaction, the positively charged ${\text{C}}{{\text{l}}^ + }$ attacks the carbon-carbon double bond. This results in formation of a carbocation intermediate ${\text{C}}{{\text{H}}_3} - {\text{C}}{{\text{H}}^ + } - {\text{C}}{{\text{H}}_2} - {\text{Cl}}$.
In the second step of the reaction, the nucleophile ${\text{O}}{{\text{H}}^ - }$ attacks the positively charged carbon atom. The final product obtained is ${\text{C}}{{\text{H}}_3} - {\text{CH}}\left( {{\text{OH}}} \right) - {\text{C}}{{\text{H}}_2} - {\text{Cl}}$.
Thus, the reaction of propene with ${\text{HOCl }}\left( {{\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}} \right)$ proceeds through the intermediate ${\text{C}}{{\text{H}}_3} - {\text{C}}{{\text{H}}^ + } - {\text{C}}{{\text{H}}_2} - {\text{Cl}}$.

Thus, the correct option is (A) ${\text{C}}{{\text{H}}_3} - {\text{C}}{{\text{H}}^ + } - {\text{C}}{{\text{H}}_2} - {\text{Cl}}$.

Additional Information: The reaction in which one molecule combines with another molecule to form a larger molecule is known as an additional reaction. No products are eliminated in the addition reaction.
There are two types of addition reactions:
Electrophilic addition reaction: In electrophilic addition reaction, a positively charged species known as electrophile gets added to a molecule.
Nucleophilic addition reaction: In nucleophilic addition reaction, a negatively charged species known as nucleophile gets added to a molecule.
The product formed in the reaction is 1-chloropropan-2-ol. 1-chloropropan-2-ol is an alcohol. Thus, the reaction is a preparation reaction of alcohol.

Note: A positively charged carbon atom is known as a carbocation.
When a carbon atom carrying a positive charge is attached to only one alkyl group it is known as a primary carbocation. Thus, ${\text{C}}{{\text{H}}_3} - {\text{CH}}\left( {{\text{Cl}}} \right) - {\text{CH}}_2^ +$ is a primary carbocation.
When a carbon atom carrying a positive charge is attached to two other alkyl groups it is known as a secondary carbocation. Thus, ${\text{C}}{{\text{H}}_3} - {\text{C}}{{\text{H}}^ + } - {\text{C}}{{\text{H}}_2} - {\text{Cl}}$ is a secondary carbocation.
A secondary carbocation is more stable than the primary carbocation. Thus, ${\text{C}}{{\text{H}}_3} - {\text{C}}{{\text{H}}^ + } - {\text{C}}{{\text{H}}_2} - {\text{Cl}}$ is formed as an intermediate.