In but-1, 3-diene the `C_(2)-C_(3)` bond length is

Options

A. 135 pm
B. 120 pm
C. 146 pm
D. 154 pm.

Explanation

To determine the bond length of the C2-C3 bond in but-1,3-diene, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of But-1,3-diene**:
- But-1,3-diene has the following structure:
```
H2C=CH-CH=CH2
```
- The carbon atoms are numbered from 1 to 4, with double bonds between C1 and C2, and C3 and C4.

2. **Locate the C2-C3 Bond**:
- The bond in question is between the second and third carbon atoms (C2 and C3). In the structure, this bond is a single bond.

3. **Understand Resonance in But-1,3-diene**:
- The presence of double bonds in the molecule allows for resonance. The electrons can be delocalized, which means that the C2-C3 bond does not behave purely as a single bond.
- This resonance leads to a bond that has characteristics of both single and double bonds.

4. **Determine Bond Lengths**:
- The typical bond lengths are as follows:
- A pure C-C single bond has a bond length of approximately 154 picometers.
- A pure C=C double bond has a bond length of approximately 133 picometers.

5. **Calculate the Effective Bond Length**:
- Due to resonance, the C2-C3 bond length will be between that of a single and a double bond.
- The effective bond length can be estimated to be around 146 picometers.

6. **Conclusion**:
- Therefore, the bond length of the C2-C3 bond in but-1,3-diene is approximately **146 picometers**.

### Final Answer:
The bond length of the C2-C3 bond in but-1,3-diene is **146 picometers**.