If the molecular formula of an organic compound is `C_10H_18`. It is:

Options

A. alkene
B. alkane
C. alkyne
D. Not a hydrocarbon

Answer

To determine the type of organic compound with the molecular formula \( C_{10}H_{18} \), we can follow these steps:

### Step 1: Identify the Degree of Unsaturation
The degree of unsaturation (DU) can be calculated using the formula:
\[ \text{DU} = \frac{(2C + 2 - H)}{2} \]
where \( C \) is the number of carbon atoms and \( H \) is the number of hydrogen atoms.

For our compound:
- \( C = 10 \)
- \( H = 18 \)

Substituting these values into the formula:
\[ \text{DU} = \frac{(2 \times 10 + 2 - 18)}{2} = \frac{(20 + 2 - 18)}{2} = \frac{4}{2} = 2 \]

### Step 2: Interpret the Degree of Unsaturation
A degree of unsaturation of 2 indicates that the compound can have:
- 2 double bonds, or
- 1 triple bond, or
- A combination of double and single bonds.

### Step 3: Determine the Type of Hydrocarbon
1. **Alkane**: Alkanes have the general formula \( C_nH_{2n+2} \). For \( C_{10} \), it would be \( H_{22} \). Since we have \( H_{18} \), it cannot be an alkane.

2. **Alkene**: Alkenes have the general formula \( C_nH_{2n} \). For \( C_{10} \), it would be \( H_{20} \). Since we have \( H_{18} \), it indicates that there is at least one double bond, making it possible to be an alkene.

3. **Alkyne**: Alkynes have the general formula \( C_nH_{2n-2} \). For \( C_{10} \), it would be \( H_{18} \). This matches our compound, indicating it could also be an alkyne.

### Step 4: Final Conclusion
Given that the degree of unsaturation is 2, and both alkenes and alkynes fit the criteria, we conclude that the compound \( C_{10}H_{18} \) can be either an alkene or an alkyne. However, since the question asks for the classification and does not specify further, we can state:

**The compound \( C_{10}H_{18} \) is either an alkene or an alkyne.**