GUJCET 2025 Chemistry Paper

Concept:Reaction of a ketone $R'R''C=O$ with a Grignard reagent $R'''\mathrm{MgX}$ followed by hydrolysis gives a tertiary alcohol, where the carbinol carbon bears $R'$, $R''$, and $R'''$.Explanation:The product is $2$-methylbutane-2-ol.Its structure is $\mathrm{CH_3-C(OH)(CH_3)-CH_2-CH_3}$.The carbinol carbon is bonded to two methyl groups and one ethyl group.So the three substituents on the product carbon are $\mathrm{CH_3}$, $\mathrm{CH_3}$, and $\mathrm{C_2H_5}$.In the reaction, these correspond to $R'=\mathrm{CH_3}$, $R''=\mathrm{C_2H_5}$, and $R'''=\mathrm{CH_3}$.This matches the reaction of butan-2-one $\mathrm{CH_3COC_2H_5}$ with $\mathrm{CH_3MgBr}$.Hence option B is correct.Answer:$R'=\mathrm{CH_3}$, $R''=\mathrm{C_2H_5}$, $R'''=\mathrm{CH_3}$.