Question

Propylene on hydrolysis with sulphuric acid forms
A. n-propyl alcohol
B. Isopropyl alcohol
C. Ethyl alcohol
D. Butyl alcohol

Answer 1

Hint: Alkenes react with dilute sulphuric acid to give alcohol. It is a hydration process where the addition of water to the alkene molecule takes place and the product formed will be alcohol. But pure water does not ionise so alkene does not react with it, thus some amount of acid is added to the water.

Complete Step by Step Answer:
On hydrolysis of alkene, the water molecule gets added to the alkene, and alcohol is formed. Since it is an addition reaction, this reaction will follow Markovnikov's law.

According to the addition mechanism of the alkene as the formation of carbocation takes place first the electrophile gets attached to the carbon which contains more no. of hydrogen atoms attached to the carbon and then the nucleophile gets attached to the carbon that contains less number of hydrogen atoms because according to markovnikov’s rule the nucleophile will attach with the carbon which contains less number of hydrogen.

In the addition reaction of alkene, the pi(π) bond between the two carbons of alkene breaks and they form two sigma bonds with two separate chemical species.
$CH_3-CH=CH_2 +\ \ dil.\ H_2SO_4\ \ \ \rightarrow CH_3-CH(OH)-CH_3$

Mechanism of the reaction:


In the given reaction the nucleophile formed is the HSO₄^― ion which attacks the formed carbocation which contains the least number of hydrogen atoms. Thus on hydrolysis of propylene in presence of sulphuric acid isopropyl alcohol is formed.
Thus, Option (B) is correct

Note: In the given reaction sulphuric acid acts as a catalyst. During hydrolysis of alkene sometimes a mixture of alcohol also formed. The major alcohol formed will be from Markovnikov rule.