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 bond between the second carbon (C2) and the third carbon (C3) in vinyl acetylene, we can follow these steps:

### Step-by-Step Solution:

1. **Draw the Structure of Vinyl Acetylene**:
- The molecular formula is CH≡C-CH=CH2.
- This structure consists of a terminal triple bond between the first and second carbon atoms, and a double bond between the third and fourth carbon atoms.

2. **Identify the Carbon Atoms**:
- According to IUPAC naming, we assign numbers to the carbon atoms:
- C1 (first carbon) is the one connected to the hydrogen and involved in the triple bond.
- C2 (second carbon) is the one involved in the triple bond with C1.
- C3 (third carbon) is involved in the double bond with C4.
- C4 (fourth carbon) is connected to two hydrogens.

3. **Determine Hybridization**:
- **For C2**:
- C2 forms three sigma bonds (one with C1 and two with C3).
- Therefore, its steric number is 3, indicating that C2 is **sp² hybridized**.
- **For C3**:
- C3 forms two sigma bonds (one with C2 and one with C4) and has two pi bonds (the double bond with C4).
- Therefore, its steric number is 2, indicating that C3 is **sp hybridized**.

4. **Determine the Type of Overlapping**:
- The bond between C2 and C3 involves the overlap of an sp² hybrid orbital from C2 and an sp hybrid orbital from C3.
- Thus, the type of overlapping in the C2-C3 bond is **sp² to sp**.

5. **Select the Correct Option**:
- Based on the analysis, the correct answer is **sp² to sp**, which corresponds to option number 1.

### Final Answer:
The type of overlapping in the C2-C3 bond is **sp² to sp**.