From amongst the following alcohols the one that would react fastest with conc. $\text{HCl}$ and anhydrous ${\text{ZnCl}}_2$, is:

The reaction of alcohols with conc. $\text{HCl}$ and anhydrous ${\text{ZnCl}}_2$ (Lucas reagent) proceeds via a carbocation intermediate.Reactivity order: $3^{\circ }>2^{\circ }>1^{\circ }$ alcohols.2–Butanol: $2^{\circ }$ 2–Methylpropan–2–ol: $3^{\circ }$ (Tert-butyl alcohol)2–Methylpropanol: $1^{\circ }$ (Isobutyl alcohol)1–Butanol: $1^{\circ }$ (n-butyl alcohol)The $3^{\circ }$ alcohol reacts fastest.