The number of `pi`- bonds and `sigma`- bonds present in naphthalene are respectively

Options

A. 6, 19
B. 5, 19
C. 5, 11
D. 5, 20

Answer

To determine the number of sigma (σ) and pi (π) bonds in naphthalene, we can follow these steps:

### Step 1: Understand the Structure of Naphthalene
Naphthalene consists of two fused benzene rings. Each benzene ring has a hexagonal structure with alternating double bonds.

### Step 2: Count the Carbon Atoms
Naphthalene has a total of 10 carbon atoms. Each carbon in the structure is bonded to either another carbon or a hydrogen atom.

### Step 3: Identify the Types of Bonds
1. **Sigma Bonds (σ)**:
- Each single bond (C-C or C-H) is a sigma bond.
- Each double bond consists of one sigma bond and one pi bond.

2. **Pi Bonds (π)**:
- Each double bond contributes one pi bond.

### Step 4: Count the Sigma Bonds
- **C-H Bonds**: There are 8 hydrogen atoms in naphthalene, leading to 8 C-H sigma bonds.
- **C-C Bonds**:
- Naphthalene has 5 C-C single bonds and 5 C-C double bonds (from the fused rings).
- Each of the 5 double bonds contributes 1 sigma bond, and there are 5 additional single bonds.
- Therefore, the total number of C-C sigma bonds is 10.

**Total Sigma Bonds Calculation**:
- C-H bonds: 8
- C-C bonds: 10
- Total σ bonds = 8 + 10 = 18 σ bonds.

### Step 5: Count the Pi Bonds
- Naphthalene has 5 double bonds, and each double bond contributes 1 pi bond.

**Total Pi Bonds Calculation**:
- Total π bonds = 5 π bonds.

### Final Answer
The number of sigma bonds and pi bonds in naphthalene are respectively **18 σ bonds and 5 π bonds**.

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