Name: Isomerism in Alcohols
Uploaded: 2019-07-19
Duration: 5 min 5 s
Description: Chemical compounds that have the same chemical formulae but differ in property and arrangement of atoms in the molecule are called an isomer. Dive into this...

Question

How different classes of alcohols can be tested by Lucas test ?

Accepted Answer

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 colourless characteristic of the solution changes to a turbid, cloudy, and hazy one implies that a chloroalkane is formed. This observation is a positive indication for the Lucas test.

Primary Alcohol :The solution remains colourless unless it is subjected to heat. The solution forms an oily layer when heated. Example: 1-Pentanol.
Secondary Alcohol :The solution turns turbid and forms an oily layer in three to five minutes (varies based on the solubility). Example: 2-Pentanol.
Tertiary Alcohol : The solution turns turbid and forms an oily layer immediately. Example: 2-methyl-2-butanol.

How different classes of alcohols can be tested by Lucas test ?

Important Questions on Alcohols

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