The number of sigma (`sigma `) and pi (`pi`) bonds in pent-2-en-4-yne is :

Options

A. 11 `sigma ` bonds and 2 `pi` bonds
B. 13 `sigma ` bonds and no `pi` bonds
C. 10 `sigma `bonds and 3 `pi` bonds
D. 8 `sigma` bonds and 5` pi` bonds.

Explanation

To determine the number of sigma (σ) and pi (π) bonds in pent-2-en-4-yne, we will follow these steps:

### Step 1: Understand the Structure of Pent-2-en-4-yne
Pent-2-en-4-yne is an organic compound that consists of five carbon atoms. The "2-en" indicates that there is a double bond starting at the second carbon, and "4-yne" indicates that there is a triple bond starting at the fourth carbon.

### Step 2: Draw the Structure
1. **Draw the five carbon atoms** in a chain:
- C1 - C2 - C3 - C4 - C5

2. **Add the double bond** between C2 and C3:
- C1 - C2=C3 - C4 - C5

3. **Add the triple bond** between C4 and C5:
- C1 - C2=C3 - C4≡C5

### Step 3: Add Hydrogen Atoms
- Each carbon atom can form four bonds. We will add hydrogen atoms to satisfy the tetravalency of carbon:
- C1: 3 H (C1-H bonds)
- C2: 1 H (C2-H bond)
- C3: 1 H (C3-H bond)
- C4: 1 H (C4-H bond)
- C5: 0 H (C5 is involved in a triple bond)

The complete structure with hydrogen atoms is:
```
H H H
| | |
H--C1--C2=C3--C4≡C5
```

### Step 4: Count the Sigma Bonds
- **Single Bonds (σ bonds)**: Each single bond is a sigma bond.
- C1-C2: 1 σ
- C2-C3: 1 σ (part of the double bond)
- C3-C4: 1 σ
- C4-C5: 1 σ (part of the triple bond)
- C1-H: 3 σ (from C1)
- C2-H: 1 σ (from C2)
- C3-H: 1 σ (from C3)
- C4-H: 1 σ (from C4)

Total σ bonds = 1 (C1-C2) + 1 (C2-C3) + 1 (C3-C4) + 1 (C4-C5) + 3 (C1-H) + 1 (C2-H) + 1 (C3-H) + 1 (C4-H) = 10 σ bonds.

### Step 5: Count the Pi Bonds
- **Double Bonds (π bonds)**: Each double bond has one pi bond.
- C2=C3: 1 π bond
- **Triple Bonds (π bonds)**: Each triple bond has two pi bonds.
- C4≡C5: 2 π bonds

Total π bonds = 1 (from C2=C3) + 2 (from C4≡C5) = 3 π bonds.

### Final Answer
- The total number of sigma (σ) bonds in pent-2-en-4-yne is **10**.
- The total number of pi (π) bonds in pent-2-en-4-yne is **3**.

### Summary
- **Number of σ bonds**: 10
- **Number of π bonds**: 3