Question

Isopropyl alcohol is obtained by reacting which of the following alkenes with conc. \[{{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}}\] and \[{{\rm{H}}_{\rm{2}}}{\rm{O}}\]
A) Ethylene
B) Propylene
C) 2-methylpropene
D) Isoprene

Answer 1

Hint: The chemical representation of the compound isopropyl alcohol is \[{\rm{C}}{{\rm{H}}_{\rm{3}}} - {\rm{CH(OH)}} - {\rm{C}}{{\rm{H}}_{\rm{3}}}\] . Now, we have to identify the alkene that gives isopropyl alcohol on reaction with conc. Sulphuric acid.

Complete Step by Step Answer:
Let’s discuss the options one by one.
Option A is ethylene (Ethene). The chemical representation of ethene is \[{\rm{C}}{{\rm{H}}_{\rm{2}}} = {\rm{C}}{{\rm{H}}_{\rm{2}}}\] . But, in the isopropyl alcohol, there is the presence of three atoms of carbon. So, A does not give isopropyl alcohol when it reacts with conc. sulphuric acid.

Option C is 2-methyl propene. The chemical representation of 2-methyl propene is \[{{\rm{H}}_{\rm{3}}}{\rm{C}} - {\rm{HC(C}}{{\rm{H}}_{\rm{3}}}{\rm{)}} - {\rm{C}}{{\rm{H}}_{\rm{3}}}\] . So, there is a methyl substituent in C2. But, in isopropyl alcohol, there is no methyl substituent. Therefore, 2-methylpropene also does not give isopropyl alcohol.

Option D is isoprene. Isoprene has the chemical representation of \[{\rm{C}}{{\rm{H}}_{\rm{2}}} = {\rm{C(C}}{{\rm{H}}_{\rm{3}}}{\rm{)}} - {\rm{CH}} = {\rm{C}}{{\rm{H}}_{\rm{2}}}\] . It has five atoms of carbon in the compound. So, it does not give isopropyl alcohol when it undergoes a reaction with concentrated sulphuric acid.

Option B is propylene. The reaction of propylene with conc. Sulphuric acid gives isopropyl alcohol. The reaction happens in the following way:

Image: Formation of isopropyl alcohol
Therefore, when propylene undergoes a reaction with sulphuric acid, isopropyl alcohol forms.
Therefore, option B is right.

Note: Isopropyl alcohol is a liquid of no colour and is a useful component in many household items namely disinfectants, cleaners, hand sanitizers, etc. Its use in the pharmaceutical industry is also significant.