An unknown alcohol is treated with the "Lucas reagent" to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism?

The reaction of alcohols with Lucas reagent (${\text{ZnCl}}_2+\text{conc. HCl}$) proceeds through the formation of a carbocation. The rate of the reaction depends on the stability of the carbocation.Tertiary ($3^{\circ }$) carbocations are the most stable due to inductive effects and hyperconjugation.Therefore, tertiary alcohols react fastest.Because the mechanism involves a carbocation intermediate, it follows the $S_{N}1$ pathway.