An organic compound A ( mol wt = 180) is acylated with `CH_3 COCl` to get acylated compound of mol wt. 390. What is the number of amino groups present per molecule of the compound A?

Options

A. 5
B. 4
C. 6
D. 2

Answer

To solve the problem, we need to determine the number of amino groups present in the organic compound A, which has a molecular weight of 180 g/mol, and is acylated with acetyl chloride (CH3COCl) to yield a product with a molecular weight of 390 g/mol.

### Step-by-Step Solution:

1. **Identify the Molecular Weights**:
- Molecular weight of compound A = 180 g/mol
- Molecular weight of the acylated compound = 390 g/mol

2. **Calculate the Difference in Molecular Weight**:
- Difference in molecular weight due to acylation = 390 g/mol - 180 g/mol = 210 g/mol

3. **Determine the Contribution of Acylation**:
- When an amino group (NH2) is acylated, it forms an amide (NHCOCH3). We need to calculate the molecular weight of the acylated group.
- The molecular weight of the acylated group (NHCOCH3) can be calculated as follows:
- NH2 contributes: Nitrogen (N) = 14 g/mol, Hydrogen (H) = 2 g/mol → Total = 16 g/mol
- Acetyl group (COCH3) contributes: Carbon (C) = 2 × 12 g/mol + Oxygen (O) = 16 g/mol + Hydrogen = 3 g/mol → Total = 24 g/mol
- Therefore, the total molecular weight of the acylated group = 16 g/mol (NH2) + 24 g/mol (COCH3) = 40 g/mol

4. **Calculate the Increase in Molecular Weight per Amino Group**:
- The increase in molecular weight when one NH2 group is acylated is given by:
- Increase = 40 g/mol - 16 g/mol = 24 g/mol

5. **Determine the Number of Amino Groups**:
- Now, we know that the total increase in molecular weight due to acylation is 210 g/mol.
- Let 'n' be the number of amino groups in compound A. The equation can be set up as:
- n × 24 g/mol = 210 g/mol
- Solving for n gives:
- n = 210 g/mol / 24 g/mol = 8.75

6. **Conclusion**:
- Since the number of amino groups must be a whole number, we round down to the nearest whole number, which is 8. Therefore, the number of amino groups present per molecule of compound A is 8.

### Final Answer:
The number of amino groups present per molecule of compound A is **8**.