The number of structural isomers for `C_(5)H_(10)` are:

Options

A. 8
B. 6
C. 9
D. 10

Answer

To determine the number of structural isomers for the molecular formula \( C_5H_{10} \), we will follow these steps:

### Step 1: Identify the Type of Compound
The formula \( C_5H_{10} \) indicates that this compound is an alkene or a cycloalkane since it follows the general formula for alkenes \( C_nH_{2n} \) (where \( n = 5 \)) or cycloalkanes.

### Step 2: Consider Alkenes
First, we will consider the structural isomers that can be formed by alkenes (with one double bond).

1. **Straight-chain alkenes**:
- **Pent-1-ene**: CH2=CH-CH2-CH2-CH3
- **Pent-2-ene**: CH3-CH=CH-CH2-CH3 (two geometric isomers: cis and trans)
- **Pent-3-ene**: CH3-CH2-CH=CH-CH3

2. **Branched-chain alkenes**:
- **2-Methylbut-1-ene**: CH2=C(CH3)-CH2-CH3
- **3-Methylbut-1-ene**: CH2=CH-CH(CH3)-CH3
- **2-Methylbut-2-ene**: CH3-C(CH3)=CH-CH3 (two geometric isomers: cis and trans)
- **Cyclopentane**: This is a cyclic structure that can also be considered.

### Step 3: Consider Cycloalkanes
Next, we will consider the cyclic structures:
1. **Cyclopentane**: C5H10 (a ring structure)
2. **Methylcyclobutane**: A 4-membered ring with one methyl substituent.
3. **Dimethylcyclopropane**: Two methyl groups on a 3-membered ring.

### Step 4: Count All Isomers
Now we will count all the isomers:
- **Alkenes**:
- Pent-1-ene
- Pent-2-ene (cis and trans)
- Pent-3-ene
- 2-Methylbut-1-ene
- 3-Methylbut-1-ene
- 2-Methylbut-2-ene (cis and trans)

This gives us a total of 8 alkenes.

- **Cycloalkanes**:
- Cyclopentane
- Methylcyclobutane
- Dimethylcyclopropane

This gives us a total of 3 cycloalkanes.

### Final Count
Adding both types together:
- Total structural isomers = 8 (alkenes) + 3 (cycloalkanes) = **11 structural isomers**.

### Conclusion
The total number of structural isomers for \( C_5H_{10} \) is **11**.

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