Total number of `sigma`-bond present in the molecula of propyne is

Explanation

To determine the total number of sigma bonds in the molecule of propyne (C3H4), we can follow these steps:

### Step 1: Understand the structure of propyne
Propyne is an alkyne with the molecular formula C3H4. Its structure can be represented as:
```
H H
\ /
C
/ \
C C
\ /
C
```
In a more detailed representation, propyne has a terminal triple bond between two carbon atoms:
```
H H
\ /
C ≡ C
/
C
```

### Step 2: Identify the types of bonds in propyne
- In propyne, there is one triple bond between two carbon atoms (C≡C).
- A triple bond consists of one sigma bond and two pi bonds.
- There are also single bonds between carbon and hydrogen atoms (C-H).

### Step 3: Count the sigma bonds
1. **Triple bond (C≡C)**: Contributes 1 sigma bond.
2. **C-H bonds**: Each carbon atom is bonded to hydrogen atoms.
- The terminal carbon (C) is bonded to one hydrogen (H).
- The middle carbon (C) is bonded to one hydrogen (H).
- The other terminal carbon (C) is bonded to three hydrogens (H).

Thus, the C-H bonds are:
- 1 (from the terminal carbon) + 1 (from the middle carbon) + 3 (from the other terminal carbon) = 5 C-H sigma bonds.

### Step 4: Total sigma bonds
Now, we can sum the sigma bonds:
- 1 sigma bond from the triple bond (C≡C)
- 5 sigma bonds from the C-H bonds

Total = 1 + 5 = 6 sigma bonds.

### Final Answer
The total number of sigma bonds present in the molecule of propyne is **6**.

---