Question

The alcohol that produces turbidity immediately with $ZnC{l}_2/Conc.HCl$ at room temperature:

• A. hydroxybutane
• B. 2-hydroxybutane
• C. 2-hydroxy-2-methylpropane
• D. 1-hydroxy-2-methylpropane

Answer 1

Answer: (C)

2-hydroxy-2-methylpropane

A solution of $ZnC{l}_2/Conc.HCl$ is called Luca's reagent. Now 2 - Hydroxy - 2 - methyl propane is a tertiary alcohol and therefore immediately produces turbidity (cloudy) on reaction with Luca's reagent. This reaction in which the -Cl group replaces the -OH group can be written as:
$C{H}_3-\left(C{H}_3\right)C\left(OH\right)-C{H}_3+HCl\to C{H}_3-\left(C{H}_3\right)C\left(Cl\right)-C{H}_3+H_{2}O$