An alkane `(A)` having a molecular mass of 72 produces one monochlorination product. Compound `(A)` is:

Options

A.
B.
C.
D.

Explanation

To solve the problem of identifying the alkane `(A)` with a molecular mass of 72 that produces only one monochlorination product, we can follow these steps:

### Step 1: Determine the molecular formula of the alkane
The general molecular formula for alkanes is given by:
\[ C_nH_{2n+2} \]
Where \( n \) is the number of carbon atoms.

### Step 2: Set up the equation based on the molecular mass
The molecular mass of carbon (C) is 12 g/mol and that of hydrogen (H) is 1 g/mol. Therefore, the molecular mass of the alkane can be expressed as:
\[ \text{Molecular mass} = 12n + (2n + 2) \]
Given that the molecular mass is 72, we can set up the equation:
\[ 12n + 2n + 2 = 72 \]
This simplifies to:
\[ 14n + 2 = 72 \]

### Step 3: Solve for \( n \)
Subtract 2 from both sides:
\[ 14n = 70 \]
Now divide by 14:
\[ n = 5 \]

### Step 4: Write the molecular formula
Using the value of \( n \):
\[ \text{Molecular formula} = C_5H_{2(5)+2} = C_5H_{12} \]

### Step 5: Identify possible structural isomers
The alkane with the formula \( C_5H_{12} \) can exist in several structural forms (isomers). The possible isomers are:
1. Pentane (n-pentane)
2. Isopentane (2-methylbutane)
3. Neopentane (2,2-dimethylpropane)

### Step 6: Analyze monochlorination products
Monochlorination of these isomers will yield different products:
- **n-Pentane**: Can produce 3 different monochlorination products.
- **Isopentane**: Can produce 4 different monochlorination products.
- **Neopentane**: All hydrogen atoms are equivalent, leading to only 1 unique monochlorination product.

### Conclusion
Since we need an alkane that produces only one monochlorination product, the compound `(A)` must be **neopentane (2,2-dimethylpropane)**.

### Final Answer
Compound `(A)` is **neopentane (C5H12)**.

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