The number of `sigma-and pi` bonds present in pent-4-en-1-yne is :

Options

A. `10,3`
B. `3,10`
C. `4,9`
D. `9,4.`

Explanation

To determine the number of sigma and pi bonds in pent-4-en-1-yne, we will follow these steps:

### Step 1: Draw the Structure of Pent-4-en-1-yne
- **Pent-4-en-1-yne** indicates that there are five carbon atoms (pent) in the chain.
- The "1-yne" indicates a triple bond at the first carbon, and "4-en" indicates a double bond at the fourth carbon.
- Therefore, the structure can be drawn as follows:

```
H H H
| | |
H--C≡C--C=C--C--H
| | |
H H H
```

### Step 2: Identify the Types of Bonds
- In the structure, we have:
- A **triple bond** between the first and second carbon atoms (C≡C).
- A **double bond** between the fourth and fifth carbon atoms (C=C).
- Single bonds between the remaining carbon atoms and the hydrogen atoms.

### Step 3: Count the Sigma Bonds
- **Single Bonds**: Each single bond contributes 1 sigma bond.
- **Double Bonds**: Each double bond contributes 1 sigma bond and 1 pi bond.
- **Triple Bonds**: Each triple bond contributes 1 sigma bond and 2 pi bonds.

Now, let's count:
- **Triple Bond (C≡C)**: 1 sigma bond.
- **Double Bond (C=C)**: 1 sigma bond.
- **Single Bonds**:
- Between C1 and C2: 1 sigma bond.
- Between C2 and C3: 1 sigma bond.
- Between C3 and C4: 1 sigma bond.
- Between C4 and C5: 1 sigma bond.
- Each carbon is bonded to hydrogen atoms (C-H bonds): 5 C-H bonds contribute 5 sigma bonds.

Total sigma bonds:
- 1 (from C≡C) + 1 (from C=C) + 4 (from C-C single bonds) + 5 (from C-H bonds) = **11 sigma bonds**.

### Step 4: Count the Pi Bonds
- **Triple Bond (C≡C)**: 2 pi bonds.
- **Double Bond (C=C)**: 1 pi bond.

Total pi bonds:
- 2 (from C≡C) + 1 (from C=C) = **3 pi bonds**.

### Final Answer
- The total number of sigma bonds in pent-4-en-1-yne is **11**.
- The total number of pi bonds in pent-4-en-1-yne is **3**.

### Summary
- **Sigma Bonds**: 11
- **Pi Bonds**: 3

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