The Lucas reagent will react fastest with:

The correct answer is Option (1) → \(\mathrm{(CH_3)_3COH}\)

Lucas reagent is concentrated HCl with anhydrous \( \ce{ZnCl2} \). The reaction goes through a carbocation: \( \ce{ZnCl2} \) helps the –OH group leave, and the more stable the carbocation, the faster the reaction. Carbocation stability, and so the rate, is tertiary > secondary > primary:

    \( \displaystyle \ce{(CH3)3C-OH + HCl} \xrightarrow{\text{anhyd. }\ce{ZnCl2}} \ce{(CH3)3C-Cl + H2O} \)

Classifying the four alcohols:

• \( \ce{(CH3)3COH} \): 2-methylpropan-2-ol, tertiary.

• \( \ce{CH3CH(CH3)OH} \): propan-2-ol, secondary.

• \( \ce{CH3CH2OH} \) and \( \ce{CH3(CH2)2OH} \): ethanol and propan-1-ol, primary.

So Lucas reagent reacts fastest with \( \ce{(CH3)3COH} \).

NCERT (2026-27 edition):
Chemical Reactions – …