Lucas Test

 Primary, Secondary, and Tertiary Alcohols are classified based on their reactivity with the Lucas reagent. The reaction that occurs in the Lucas test can be seen as a nucleophilic substitution reaction. In this reaction, the Chloride in the zinc-chloride bond is replaced with a hydroxyl group originating from the given alcohol.

The reaction displays the difference in reactivity of the different types of alcohol as well as the difference in the ease at which corresponding carbocations of the alcohols are formed. For example, primary alcohols do not react readily at room temperature with the added Lucas reagent whereas tertiary alcohols react immediately.

The observation of a change where the clear and colorless characteristic of the solution changes to a turbid, cloudy, and hazy one implies that a chloroalkane has formed. This observation is a positive indication for the Lucas test.

Primary, Secondary, and Tertiary alcohols react with the Lucas reagent to form chloroalkane at different rates. Tertiary alcohols react the fastest due to the fact that organic chloride has relatively low solubility in the aqueous mixture.