The number of all possible products excluding stereoisomers obtained on monochlorination of n-butane and iso-butane are respectively

Options

A. 2 and 3
B. 3 and 2
C. 2 and 1
D. 2 and 2

Answer

To solve the problem of determining the number of possible monochlorination products (excluding stereoisomers) for n-butane and iso-butane, we can follow these steps:

### Step 1: Understand the Structures
- **n-Butane** (C4H10) has the structure: CH3-CH2-CH2-CH3.
- **Iso-butane** (or 2-methylpropane, C4H10) has the structure: (CH3)2CH-CH3.

### Step 2: Identify Chlorination Sites for n-Butane
- In n-butane, there are two types of hydrogen atoms:
- **Primary Hydrogens**: 6 (on the terminal CH3 groups)
- **Secondary Hydrogens**: 4 (on the two CH2 groups)

- When monochlorination occurs, chlorine can replace a hydrogen atom at any of these positions.

### Step 3: Count the Unique Products for n-Butane
- **Chlorination at Primary Positions**:
- Replacing a primary hydrogen gives the same product (1-chlorobutane).

- **Chlorination at Secondary Positions**:
- Replacing a secondary hydrogen gives a different product (2-chlorobutane).

- Thus, for n-butane, the unique monochloro products are:
1. 1-chlorobutane
2. 2-chlorobutane

### Step 4: Identify Chlorination Sites for Iso-Butane
- In iso-butane, the chlorination sites are:
- **Tertiary Hydrogen**: 1 (on the central carbon)
- **Primary Hydrogens**: 6 (on the two terminal CH3 groups)

### Step 5: Count the Unique Products for Iso-Butane
- **Chlorination at Tertiary Position**:
- Replacing the tertiary hydrogen gives 2-chloro-2-methylpropane.

- **Chlorination at Primary Positions**:
- Replacing any of the primary hydrogens gives the same product (1-chloro-2-methylpropane).

- Thus, for iso-butane, the unique monochloro products are:
1. 1-chloro-2-methylpropane
2. 2-chloro-2-methylpropane

### Step 6: Conclusion
- The number of unique monochloro products for n-butane is **2**.
- The number of unique monochloro products for iso-butane is **2**.
- Therefore, the final answer is **2 and 2**.

### Final Answer
The number of all possible products excluding stereoisomers obtained on monochlorination of n-butane and iso-butane are respectively **2 and 2**.

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