A mixture of 1-chlorobutane and 2-chlorobutane when treated with alcoholic KOH gives:

Options

A. 1-butene
B. 2-butene
C. isobutylene
D. mixture of 1-butene + 2 butene

Answer

To solve the problem of what products are formed when a mixture of 1-chlorobutane and 2-chlorobutane is treated with alcoholic KOH, we can follow these steps:

### Step 1: Identify the Reactants
We have two reactants:
1. **1-chlorobutane (C4H9Cl)**: This has the structure CH3-CH2-CH2-CH2-Cl.
2. **2-chlorobutane (C4H9Cl)**: This has the structure CH3-CH2-CH(Cl)-CH3.

### Step 2: Understand the Reaction Condition
The reaction is carried out in the presence of alcoholic KOH. Alcoholic KOH is a strong base that promotes elimination reactions, specifically beta-elimination (dehydrohalogenation), where HX (in this case, HCl) is eliminated.

### Step 3: Analyze the Reaction of 1-chlorobutane
For **1-chlorobutane**:
- The chlorine atom is attached to the first carbon (alpha carbon).
- The beta carbon is the second carbon.
- When KOH acts on 1-chlorobutane, it will remove a hydrogen atom from the beta carbon (C2) and eliminate HCl.

The reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Cl} + \text{KOH} \rightarrow \text{CH}_3\text{CH}_2\text{CH}=\text{CH}_2 + \text{HCl} \]

The product formed is **but-1-ene** (C4H8).

### Step 4: Analyze the Reaction of 2-chlorobutane
For **2-chlorobutane**:
- The chlorine atom is attached to the second carbon (alpha carbon).
- There are two beta carbons (C1 and C3).
- KOH can remove a hydrogen atom from either beta carbon leading to two possible products.

1. If hydrogen is removed from C1:
\[ \text{CH}_3\text{CH}_2\text{CHCl}\text{CH}_3 + \text{KOH} \rightarrow \text{CH}_3\text{CH}=\text{CH}\text{CH}_3 + \text{HCl} \]
This product is **but-2-ene** (C4H8).

2. If hydrogen is removed from C3:
\[ \text{CH}_3\text{CH}_2\text{CHCl}\text{CH}_3 + \text{KOH} \rightarrow \text{CH}_3\text{CH}_2\text{CH}=\text{CH}_2 + \text{HCl} \]
This product is also **but-2-ene** (C4H8).

### Step 5: Combine the Products
From the reactions above, we see that:
- From 1-chlorobutane, we get **but-1-ene**.
- From 2-chlorobutane, we get **but-2-ene**.

Thus, the final products when a mixture of 1-chlorobutane and 2-chlorobutane is treated with alcoholic KOH are **but-1-ene** and **but-2-ene**.

### Final Answer
The mixture of 1-chlorobutane and 2-chlorobutane when treated with alcoholic KOH gives **but-1-ene and but-2-ene**.

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