Which of the following orbital overlaps is involved in the formation of the carbon-carbon signle bond in the molecule
`HC -= C - CH = CH_(2)` ?

Options

A. (1) `sp^(3) - sp^(3)`
B. (2) `sp^(2) - sp^(3)`
C. (3) `sp - sp^(2)`
D. (4) `sp^(3) - sp`

Explanation

To determine the type of orbital overlap involved in the formation of the carbon-carbon single bond in the molecule \( HC \equiv C - CH = CH_2 \), we can follow these steps:

### Step 1: Identify the Structure of the Molecule
The given molecule is \( HC \equiv C - CH = CH_2 \). It contains a carbon-carbon triple bond between the first two carbon atoms and a carbon-carbon double bond between the last two carbon atoms.

### Step 2: Identify the Hybridization of Each Carbon Atom
1. **C1 (first carbon)**: This carbon is involved in a triple bond with C2 and a single bond with H.
- **Steric Number**: 2 (1 triple bond with C2 and 1 single bond with H)
- **Hybridization**: Since the steric number is 2, the hybridization is \( sp \).

2. **C2 (second carbon)**: This carbon is involved in a triple bond with C1 and a single bond with C3.
- **Steric Number**: 3 (1 triple bond with C1 and 1 single bond with C3)
- **Hybridization**: Since the steric number is 3, the hybridization is \( sp^2 \).

3. **C3 (third carbon)**: This carbon is involved in a single bond with C2 and a double bond with C4.
- **Steric Number**: 3 (1 single bond with C2 and 1 double bond with C4)
- **Hybridization**: Since the steric number is 3, the hybridization is \( sp^2 \).

4. **C4 (fourth carbon)**: This carbon is involved in a double bond with C3 and two single bonds with H.
- **Steric Number**: 3 (1 double bond with C3 and 2 single bonds with H)
- **Hybridization**: Since the steric number is 3, the hybridization is \( sp^2 \).

### Step 3: Identify the Overlap in the Carbon-Carbon Single Bond
The carbon-carbon single bond in the molecule is between C2 and C3.
- C2 has \( sp^2 \) hybridization.
- C3 also has \( sp^2 \) hybridization.

### Step 4: Determine the Type of Orbital Overlap
The overlap that forms the single bond between C2 and C3 is between the \( sp^2 \) hybrid orbital of C2 and the \( sp^2 \) hybrid orbital of C3.

### Conclusion
Thus, the orbital overlap involved in the formation of the carbon-carbon single bond in the molecule \( HC \equiv C - CH = CH_2 \) is \( sp^2 - sp^2 \) overlap.

### Final Answer
The correct option is: **\( sp^2 - sp^2 \) orbital overlap.**

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