Amongst the following alcohols which would react fastest conc. HCl and `ZnCl_(2)` ?

Options

A. 2-Methylbutan-1-ol
B. 2-Pentanol
C. 1- Pentanol
D. 2-Methyl-2-butanol

Answer

To determine which alcohol reacts fastest with concentrated HCl and ZnCl₂ (Lucas reagent), we need to analyze the reactivity of the given alcohols based on their structure. The reactivity order of alcohols with Lucas reagent is tertiary (3°) > secondary (2°) > primary (1°).

Let's break down the steps:

### Step 1: Identify the Structures of the Alcohols
1. **2-Methyl-1-butanol** (1° alcohol)
- Structure: CH₃-CH(CH₃)-CH₂-CH₂OH
2. **2-Pentanol** (2° alcohol)
- Structure: CH₃-CH(OH)-CH₂-CH₂-CH₃
3. **1-Pentanol** (1° alcohol)
- Structure: CH₃-CH₂-CH₂-CH₂-CH₂OH
4. **2-Methyl-2-butanol** (3° alcohol)
- Structure: CH₃-C(OH)(CH₃)-CH₂-CH₃

### Step 2: Determine the Degree of Each Alcohol
- **2-Methyl-1-butanol**: Primary (1°) alcohol
- **2-Pentanol**: Secondary (2°) alcohol
- **1-Pentanol**: Primary (1°) alcohol
- **2-Methyl-2-butanol**: Tertiary (3°) alcohol

### Step 3: Apply the Reactivity Order
According to the reactivity order with Lucas reagent:
- Tertiary alcohols react fastest, followed by secondary, and primary alcohols react the slowest or may not react at all.

### Step 4: Conclusion
Among the given alcohols, **2-Methyl-2-butanol** is a tertiary alcohol and will react the fastest with concentrated HCl and ZnCl₂.

### Final Answer
The alcohol that would react fastest with concentrated HCl and ZnCl₂ is **2-Methyl-2-butanol**.

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