But- 2-yne contains :

Options

A. sp hybridised carbon atoms only
B. `sp^(3)` hybridised carbon atoms only
C. both sp and `sp^(2)` hybridised carbon atoms
D. both sp and `sp^(3)` hybridised carbon atoms

Answer

To determine the hybridization of the carbon atoms in but-2-yne, we will follow a systematic approach.

### Step-by-Step Solution:

1. **Identify the Structure of But-2-yne**:
- But-2-yne has the molecular formula C₄H₆.
- The name indicates that it is a 4-carbon alkyne with a triple bond between the second and third carbon atoms.
- The structure can be represented as:
\[ CH_3 - C \equiv C - CH_3 \]

2. **Draw the Lewis Structure**:
- The Lewis structure for but-2-yne is:
\[ CH_3 - C \equiv C - CH_3 \]
- Here, the first and last carbon atoms (C1 and C4) are connected to three hydrogen atoms and one carbon atom, while the middle two carbon atoms (C2 and C3) are connected to each other with a triple bond.

3. **Determine the Hybridization of Each Carbon Atom**:
- **Carbon 1 (C1)**:
- It forms 4 sigma bonds (3 with H and 1 with C2).
- Steric number = 4 (4 sigma bonds, no lone pairs).
- Hybridization = sp³.
- **Carbon 2 (C2)**:
- It forms 1 sigma bond with C1 and 1 sigma bond with C3, plus 2 pi bonds from the triple bond.
- Steric number = 2 (1 sigma bond and 1 triple bond contributes 1 sigma and 2 pi).
- Hybridization = sp.
- **Carbon 3 (C3)**:
- It forms 1 sigma bond with C2 and 1 sigma bond with C4, plus 2 pi bonds from the triple bond.
- Steric number = 2 (1 sigma bond and 1 triple bond contributes 1 sigma and 2 pi).
- Hybridization = sp.
- **Carbon 4 (C4)**:
- It forms 4 sigma bonds (3 with H and 1 with C3).
- Steric number = 4 (4 sigma bonds, no lone pairs).
- Hybridization = sp³.

4. **Summarize the Hybridization**:
- C1: sp³
- C2: sp
- C3: sp
- C4: sp³

5. **Identify the Types of Hybridization Present**:
- The molecule contains both sp and sp³ hybridized carbon atoms.

### Conclusion:
The correct answer is that but-2-yne contains sp and sp³ hybridized carbon atoms.