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The Lucas test is a chemical test used to differentiate between primary, secondary, and tertiary alcohols based on their reactivity with Lucas reagent. The Lucas reagent is a mixture of concentrated hydrochloric acid (HCl) and anhydrous zinc chloride (ZnCl2). When alcohols react with this reagent, they form alkyl chlorides, which are insoluble and appear as turbidity in the solution. The speed of turbidity formation helps identify the type of alcohol.

Observation of Lucas Test:

• Tertiary Alcohols: Give turbidity immediately (within seconds).
• Secondary Alcohols: Give turbidity after 5–10 minutes.
• Primary Alcohols: Do not react at room temperature or react very slowly.

Reaction Mechanism:
Tertiary alcohols react quickly because they form stable tertiary carbocations. Secondary alcohols form less stable carbocations, so they take time. Primary alcohols hardly react as their carbocations are unstable.

Applications of Lucas Test:

• Used in organic chemistry labs to identify types of alcohols.
• Helps in classifying unknown alcohol samples.

Therefore, the Lucas test is a simple yet powerful tool in organic chemistry to distinguish alcohols based on their reactivity.