Question

Lucas test is given by an alcohol within 5 minutes. $0.22g$ of which liberates 56 mL of $C{H}_4$ at STP on treating with $C{H}_{3}MgI$. The structure of alcohol is

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

Lucas test will be given by all the given alcohols within 5 minutes as all are 2${}^{\circ }$ alcohols. Exact structure can be known by molecular mass or formula of alcohol which will be obtained as follows :
Let molecular mass of alcohol be M.
$\frac{56}{22400}=\frac{0.22}{M}$ or, $M=\frac{22400\times 0.22}{56}=88$
The general formula of alcohols is C_nH_{2n + 1}OH. The molecular mass 88 corresponds to the value of n = 5. Thus, the 2${}^{\circ }$ alcohol is (CH₃)₂CHCHOHCH₃.