Question
The compound which reacts fastest with Lucas reagent at room temperature is
A.
$${\text{butan - 1 - ol}}$$
B.
$${\text{butan - 2 - ol}}$$
C.
$${\text{2 - methylpropan - 1 - ol}}$$
D.
$${\text{2 - methylpropan - 2 - ol}}$$
Answer :
$${\text{2 - methylpropan - 2 - ol}}$$
Solution :
TIPS/Formulae :
The order of reactivity of alcohol with Lucas reagent is $$tert. > sec. > pri.$$
Lucas test is based on the difference in the three types of alcohols ( having 6 or less carbon ) towads Lucas reagent (a mixture of conc. hydrochloric acid and anhydrous zinc chloride) at room temperature.
\[ROH+HCl\xrightarrow{ZnC{{l}_{2}}}RCl+{{H}_{2}}O\]
The tertiary alcohols produce turbidity immediately,
the secondary alcohols give turbidity within 5 - 10
minutes, and the primary alcohols do not give turbidity
at all, at room temperature.
Hence \[\text{2 - methylpropan - 2 - ol}\] ( a $${3^ \circ }$$ alcohol ) reacts fastest.