Degree of unsaturation of `C_9H_12` is …............

Answer

To find the degree of unsaturation for the compound with the formula \( C_9H_{12} \), we can use the following formula:

\[ \text{Degree of Unsaturation} = \frac{(2C + 2 + N - H - X)}{2} \]

Where:
- \( C \) = number of carbon atoms
- \( H \) = number of hydrogen atoms
- \( N \) = number of nitrogen atoms
- \( X \) = number of halogen atoms (like F, Cl, Br, I)

### Step-by-Step Solution:

1. **Identify the number of carbon (C) and hydrogen (H) atoms:**
- From the formula \( C_9H_{12} \), we have:
- \( C = 9 \)
- \( H = 12 \)

2. **Identify the number of nitrogen (N) and halogen (X) atoms:**
- In this case, there are no nitrogen or halogen atoms present, so:
- \( N = 0 \)
- \( X = 0 \)

3. **Substitute the values into the formula:**
- Plugging the values into the degree of unsaturation formula:
\[ \text{Degree of Unsaturation} = \frac{(2(9) + 2 + 0 - 12 - 0)}{2} \]

4. **Calculate the expression:**
- Calculate the numerator:
\[ 2(9) + 2 + 0 - 12 - 0 = 18 + 2 - 12 = 8 \]
- Now divide by 2:
\[ \text{Degree of Unsaturation} = \frac{8}{2} = 4 \]

5. **Conclusion:**
- The degree of unsaturation for \( C_9H_{12} \) is \( 4 \).

### Final Answer:
The degree of unsaturation of \( C_9H_{12} \) is **4**.