Question

Mixture of conc. HCI and anhydrous ZnCl₂ is an important reagent which helps to distinguish between 1°, 2° and 3° alcohols.

a) Give the name of the above reagent. 

b) Give one example each for 1°, 2° & 3° alcohols. 

c) Explain how the above reagent helps to distinguish above three types of alcohols.

Answer 1

a) Lucas reagent

c) Lucas test 1°, 2° and 3° alcohols can be distin guished by Lucas test. Alcohols are soluble in Lucas reagent while their halides are immiscible and produce turbidity in solution. The dierence in reactivity of three classes of alcohols with HCI distinguishes from one another. The order of reactivity of alcohols with Lucas reagent is in the order 3°> 2°> 1°. Thus, in the case of 3°alcohols turbidity is produced immediately as they form the halides easily. In the case of 2° alcohols turbidity is produced within 5 minutes at room tem perature. In the case of 1° alcohols no turbidity is produced at room temperature since they are least reactive.