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?

Options

A. Secondary alcohol by `S_(N)1`
B. Tertiary alcohol by `S_(N)2`
C. Secondary alcohol by `S_(N)2`
D. Tertiary alcohol by `S_(N)1`

Answer

D

Explanation

The reaction of alcohol with Lucas reagent is mostly an `S_(N)1` reaction and the rate of reaction is directly proportional to the stability of carbocation formed in the reaction. Since, `3^(@)R-OH` forms `3^(@)` carbocation (most stable) hence it wil react fastest.
`underset("Tertiary alcohol")(R_(3)COH) overset("Conc. HCl") underset("Anhy. "ZnCl_(2))rarr R_(3)"CCl"+H_(2)O rarr" Turbidity appears immediately"`