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

Options

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

Explanation

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

### Step 1: Draw the Structure
1. **Identify the carbon chain**: The name "pent-1-ene-4-yne" indicates a 5-carbon chain (pent) with a double bond (ene) at the first carbon and a triple bond (yne) at the fourth carbon.
2. **Draw the carbon skeleton**: Start by drawing five carbon atoms in a row:
```
C1 - C2 - C3 - C4 - C5
```

### Step 2: Add the Double Bond
1. **Place the double bond**: At the first carbon (C1), place a double bond with the second carbon (C2):
```
C1 = C2 - C3 - C4 - C5
```

### Step 3: Add the Triple Bond
1. **Place the triple bond**: At the fourth carbon (C4), place a triple bond with the fifth carbon (C5):
```
C1 = C2 - C3 - C4 ≡ C5
```

### Step 4: Complete the Valences with Hydrogen Atoms
1. **Add hydrogen atoms**: Each carbon atom should have four bonds. Fill in the hydrogen atoms:
- C1 has 1 hydrogen (double bond with C2).
- C2 has 1 hydrogen (double bond with C1).
- C3 has 2 hydrogens (single bonds with C2 and C4).
- C4 has 1 hydrogen (triple bond with C5).
- C5 has no hydrogens (triple bond with C4).

The complete structure looks like this:
```
H H H
| | |
H - C1 = C2 - C3 - C4 ≡ C5
|
H
```

### Step 5: Count Sigma Bonds
1. **Identify the types of bonds**:
- Each single bond (C-C or C-H) is a sigma bond.
- Each double bond has 1 sigma bond and 1 pi bond.
- Each triple bond has 1 sigma bond and 2 pi bonds.

2. **Count the sigma bonds**:
- **Single bonds**: C1 to C2, C2 to C3, C3 to C4, C4 to C5, and C1 to H, C2 to H, C3 to H, C4 to H.
- Total single bonds = 8 (C-H and C-C).
- **Double bond (C1=C2)** contributes 1 sigma bond.
- **Triple bond (C4≡C5)** contributes 1 sigma bond.

Total sigma bonds = 8 (single bonds) + 1 (double bond) + 1 (triple bond) = 10 sigma bonds.

### Step 6: Count Pi Bonds
1. **Count the pi bonds**:
- The double bond (C1=C2) contributes 1 pi bond.
- The triple bond (C4≡C5) contributes 2 pi bonds.

Total pi bonds = 1 (from double bond) + 2 (from triple bond) = 3 pi bonds.

### Final Answer
- The number of sigma bonds is **10**.
- The number of pi bonds is **3**.