Question

From amongst the following alcohols the one that would react fastest with conc.HCl and anhydrous ZnCl₂, is

(a) 1-Butanol 

(b) 2-Butanol

(c) 2-Methylpropan-2-ol

(d) 2-Methylpropanol

Answer 1

(c) : The reagent, conc.HCl and anhydrous ZnCl₂ is Lucas reagent, which is used to distinguish between 1°, 2° and 3° alcohols.

3° alcohol + Lucas reagent → Immediate turbidity.
2° alcohol + Lucas reagent → Turbidity after 5 mins.

1° alcohol + Lucas reagent → No reaction.
Thus, the required alcohol is 2-methylpropan-2- ol, i.e.