The compound which gives turbidity immediately with Lucas reagent at room temperature is ______. (A) butan-2-ol (B) butan-1-ol (C) 2-methyl propan-1-ol (D) 2-methyl propan-2-ol

The compound that gives turbidity immediately with Lucas reagent at room temperature is 2-methyl propan-2-ol, also known as tert-butanol. This reaction is significant in organic chemistry, particularly in distinguishing between primary, secondary, and tertiary alcohols based on their reactivity with Lucas reagent.

Understanding Lucas Reagent

Lucas reagent is a solution of zinc chloride in hydrochloric acid, commonly used to classify alcohols. The key to its function lies in its ability to react with alcohols to form alkyl chlorides. The rate of this reaction varies significantly depending on whether the alcohol is primary, secondary, or tertiary.

Reactivity of Alcohols

• Primary Alcohols: React slowly, often requiring heat.
• Secondary Alcohols: React moderately, showing turbidity within a few minutes.
• Tertiary Alcohols: React rapidly, producing turbidity almost immediately at room temperature.

Analyzing the Options

Let’s break down the options provided:

• Butan-2-ol: This is a secondary alcohol. It will show turbidity, but not immediately.
• Butan-1-ol: This is a primary alcohol and will react very slowly, requiring heat to show turbidity.
• 2-Methyl propan-1-ol: Another primary alcohol, which also reacts slowly.
• 2-Methyl propan-2-ol: This is a tertiary alcohol and will react quickly with Lucas reagent, resulting in immediate turbidity.

Conclusion on the Correct Answer

Given the reactivity patterns of these alcohols, 2-methyl propan-2-ol is the only compound that will give turbidity immediately with Lucas reagent at room temperature. This rapid reaction is due to the stability of the tertiary carbocation formed during the reaction, which facilitates the conversion to the alkyl chloride.

In summary, when working with Lucas reagent, the classification of alcohols is crucial for predicting their behavior in reactions. Tertiary alcohols like 2-methyl propan-2-ol stand out due to their quick reactivity, making them easy to identify in laboratory settings.