The chemical formula of Lucas reagent is

Lucas reagent formula is a combination of anhydrous zinc chloride (ZnCl₂) dissolved in concentrated hydrochloric acid (HCl).

Purpose and Applications of Lucas Reagent

The Lucas reagent formula is primarily used to distinguish between primary (1°), secondary (2°), and tertiary (3°) alcohols based on their reactivity. The test involves observing the reaction of alcohols with the Lucas reagent to form alkyl halides, which appear as a turbidity in the solution.

Key Reactions

• 1° alcohols: Show no turbidity or a very slow reaction.
• 2° alcohols: Show turbidity within a few minutes.
• 3° alcohols: React immediately, forming turbidity instantly.

Preparation of Lucas Reagent

The Lucas reagent formula is prepared by dissolving anhydrous ZnCl₂ in concentrated HCl. The mixture forms a solution that is highly reactive and suitable for testing alcohols.

Example Reaction

When a tertiary alcohol reacts with the Lucas reagent:

(CH₃)₃COH + HCl → (CH₃)₃CCl + H₂O