Question

Reaction of Grignard reagent, C₂H₅MGBr with C₈H₈O followed by hydrolysis gives compound ‘A’ which reacts instantly with Lucas reagent to give compound B, C₁₀H₁₃Cl. The compound B us:

Answer 1

Hint: A Grignard reagent defines a chemical entity of the formula R-Mg-X, here, R indicates the alkyl or aryl group and X represents a halogen such as Chlorine, Bromine etc. It is one of the most useful reagents in chemistry due to its use in the manufacture of a variety of compounds.

Complete Step by Step Solution:
The reaction of ketone with the Grignard reagent gives tertiary alcohol. And when tertiary alcohol undergoes reaction with Lucas reagent, it gives alkyl chloride. Therefore, \[{{\rm{C}}_{\rm{8}}}{{\rm{H}}_{\rm{8}}}{\rm{O}}\]is a ketone.
The reaction of \[{{\rm{C}}_{\rm{8}}}{{\rm{H}}_{\rm{8}}}{\rm{O}}\]and \[{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{MgBr}}\]are shown as below,

Image: Reaction with Grignard reagent

In the above reaction, the first step is the nucleophilic attack of the C-Mg bond to the Carbonyl Carbon takes place. And in the second step, protonation occurs. In this step, negatively charged Oxygen accepts a proton and results in the formation of alcohol.

The next reaction is the reaction of formed alcohol (A) with Lucas's reagent. Lucas' reagent defines a chemical entity composed of zinc chloride solution (anhydrous form) in hydrochloric acid (concentrated form).

So, the reaction is,

Image: Reaction with Lucas reagent
When tertiary alcohol undergoes reaction with Lucas reagent, it converts into alcohol. So, B is an alkyl chloride.
Hence,the correct option is B

Note: It is to be noted that Lucas reagent is useful in differentiating between primary, tertiary and secondary alcohols. The difference between them is measured by the time required by each to make the clear solution turbid.