The compound which reacts fastest with Lucas reagent at room temperature is :

Options

A. butan-1-ol
B. butan-2-ol
C. 2-methylpropan-1-ol
D. 2-methylpropan-2-ol

Explanation

To determine which compound reacts fastest with Lucas reagent at room temperature, we need to understand the nature of the compounds involved and how they interact with the reagent.

### Step-by-Step Solution:

1. **Understand Lucas Reagent**: Lucas reagent is a mixture of hydrochloric acid (HCl) and zinc chloride (ZnCl2). It is used to differentiate between primary, secondary, and tertiary alcohols based on their reactivity.

2. **Identify Alcohol Types**:
- **Primary Alcohols (1°)**: The hydroxyl (-OH) group is attached to a carbon that is connected to only one other carbon. They react slowly with Lucas reagent and often require heating to show turbidity.
- **Secondary Alcohols (2°)**: The -OH group is attached to a carbon connected to two other carbons. They react moderately with Lucas reagent, showing turbidity in a few minutes at room temperature.
- **Tertiary Alcohols (3°)**: The -OH group is attached to a carbon connected to three other carbons. They react very quickly with Lucas reagent, showing immediate turbidity at room temperature.

3. **Analyze Given Options**:
- **Option 1: Butan-1-ol** (1° alcohol): This is a primary alcohol and will react slowly, requiring heat for turbidity.
- **Option 2: Butan-2-ol** (2° alcohol): This is a secondary alcohol and will show turbidity in a few minutes at room temperature.
- **Option 3: 2-Methylpropan-1-ol** (1° alcohol): This is also a primary alcohol and will react slowly, similar to butan-1-ol.
- **Option 4: 2-Methylpropan-2-ol** (3° alcohol): This is a tertiary alcohol and will react immediately with Lucas reagent, showing turbidity right away.

4. **Conclusion**: Among the options, the tertiary alcohol (2-Methylpropan-2-ol) will react the fastest with Lucas reagent at room temperature, producing immediate turbidity.

### Final Answer:
The compound which reacts fastest with Lucas reagent at room temperature is **2-Methylpropan-2-ol** (Option 4).

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