What is Lucas Reagent?

The correct answer is Option (3) → \(ZnCl_2\) and conc. \(HCl\)

Alcohols react with hydrogen halides to give alkyl halides. The rate of reaction with HCl depends on the class of the alcohol, because the reaction goes through a carbocation and tertiary carbocations form most easily. This difference is used in the Lucas test. Lucas reagent is concentrated HCl with anhydrous \( \ce{ZnCl2} \); the Lewis acid \( \ce{ZnCl2} \) binds to the oxygen of the –OH group and helps the C–O bond to break.

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

NCERT (2026-27 edition):
Reaction with Hydrogen Halides – …