Question

In Lucas test an alcohol reacts immediately and gives insoluble chloride. The alcohol is

• A. $C{H}_{3}OH$
• B. $C{H}_{3}C{H}_{2}OH$
• C. $(C{H}_3{)}_{2}CHOH$
• D. $(C{H}_3{)}_{3}COH$

Answer 1

Answer: (D)

Lucas test is used to distinguish between primary, secondary and tertiary alcohols A mixture of conc $HCl$+ anhy $ZnC{l}_2$ is called Lucas reagent. In Lucas test tertiary alcohols immediately give turbidity while secondary alcohols give turbidity after $5$ min. Primary alcohols give no reaction with Lucas reagent at room temperature
$\underset{\text{(Primary alcohol)}}{C{H}_{3}OH/C{H}_{3}C{H}_{2}OH}\stackrel{\mathrm{conc}\mathrm{HCl}{}^{+}\mathrm{anhy}\mathrm{ZnCl}{}_2}{\to }$ No
reaction and hence, no white cloudiness on turbidity at room temperature
$\underset{\text{(Secondary alcohol)}}{(C{H}_3{)}_{2}CHOH}\stackrel{\mathrm{conc}\mathrm{Hcl}+\mathrm{anhy}\mathrm{ZnCl}{}_2}{\to }$
White cloudiness or turbidity appears with in about $5$ min
$\underset{\text{(turboidityalcohol}}{(C{H}_3{)}_{3}COH}\stackrel{\mathrm{conc}\mathrm{HCl}{}^{+}\mathrm{anhy}\mathrm{ZnCl}{}_2}{\to }$
White cloudiness or turbidity appears immediately