Question

From amongst the following alcohols the one that would react fastest with $conc.HCl$ and anhydrous $ZnC{l}_2$, is

• A. $1$-butanol
• B. $2$-butanol
• C. $2$-methylpropan-$2$-ol
• D. $2$-methylpropanol.

Answer 1

Answer: (C)

The reagent, conc.HCl and anhydrous $ZnC{l}_2$ is Lucas reagent, which is used to distinguish between $1^{\circ }$, $2^{\circ }$ and $3^{\circ }$ alcohols.
$3^{\circ }$ alcohol + Lucas reagent $\to$ Immediate turbidity.
$2^{\circ }$ alcohol + Lucas reagent $\to$ Turbidity after 5 mins.
$1^{\circ }$ alcohol + Lucas reagent $\to$ No reaction.
The required alcohol is 2-methylpropan-2-ol, i.e.,