Question

An unknown alcohol is treated with the 'Lucas reagent' to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism?

• A. Tertiary alcohol by $S_{N}1$
• B. Secondary alcohol by $S_{N}2$
• C. Tertiary alcohol by $S_{N}2$
• D. Secondary alcohol by $S_{N}1$

Answer 1

The correct option is A Tertiary alcohol by $S_{N}1$

Lucas test in alcohol is a test to differentiate between primary, secondary and tertiary alcohols. It is based on the difference in reactivity of the three classes of alcohols with hydrogen halides. Reaction proceeds through carbocation formation as $3^0$ carbocation is highly stable. Hence, the reaction proceeds through $S_{N}1$ with $3^0$ alcohol.