In vinyl acetylene `overset(1)( C) H-=overset(2)( C)- overset(3)( C) H= overset(4) ( C) H_2 `, type of overlapping in `(C_2 underline(sigma) C_3)` bond is :

Options

A. `sp^2 - sp`
B. `sp- sp^2`
C. `sp^3-sp^3`
D. `sp^3-sp^2`

Answer

To determine the type of overlapping in the C2-C3 sigma bond in vinyl acetylene, we will follow these steps:

### Step 1: Understand the Structure of Vinyl Acetylene
Vinyl acetylene has the following structure:
```
H H
| |
H-C=C-C≡C-H
| |
H H
```
Here, we need to analyze the bond between carbon atoms C2 and C3.

### Step 2: Identify the Hybridization of Each Carbon Atom
To find the hybridization, we will calculate the steric number for each carbon atom. The steric number is calculated as follows:
- Steric number = (Number of sigma bonds) + (Number of lone pairs) + (Number of coordinate bonds)

#### Carbon 1 (C1):
- Forms 1 sigma bond with H and 1 sigma bond with C2.
- Steric number = 2 (2 sigma bonds, no lone pairs).
- Hybridization = sp.

#### Carbon 2 (C2):
- Forms 1 sigma bond with C1 and 1 sigma bond with C3.
- Steric number = 2 (2 sigma bonds, no lone pairs).
- Hybridization = sp.

#### Carbon 3 (C3):
- Forms 1 sigma bond with C2, 1 sigma bond with C4, and 1 pi bond with C4 (not counted in steric number).
- Steric number = 3 (3 sigma bonds, no lone pairs).
- Hybridization = sp².

#### Carbon 4 (C4):
- Forms 1 sigma bond with C3 and 2 sigma bonds with H atoms.
- Steric number = 3 (3 sigma bonds, no lone pairs).
- Hybridization = sp².

### Step 3: Determine the Type of Overlapping in C2-C3 Bond
The bond between C2 and C3 is a sigma bond. The hybridization types of C2 and C3 are:
- C2: sp
- C3: sp²

The overlapping type for the sigma bond formed between an sp hybridized carbon and an sp² hybridized carbon is referred to as **sp-sp² overlapping**.

### Step 4: Conclusion
The type of overlapping in the C2-C3 sigma bond is **sp-sp² overlapping**.