Question

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

• A. $2-methyl-propan-2-ol$
• B. $2-Butanol$
• C. $1-Butanol$
• D. $2-methylpropanol$

Answer 1

The correct option is A $2-methyl-propan-2-ol$

The alcohol that would react fastest with $conc.HCl$ and anhydrous $ZnC{l}_2$, is $2-methyl-propan-2-ol$. It is a tertiary alcohol.
A mixture of $conc.HCl$ and anhydrous $ZnC{l}_2$ is called Lucas reagent.
Primary alcohols react with Lucas reagent very slowly on heating to give alkyl chlorides.
Secondary alcohols react with Lucas reagent much faster.
Tertiary alcohols instantaneously react with HCl at room temperature.
Note: Lucas reagent is required for primary and secondary alcohol only.