In which compound C–Cl bond length is shortest

Options

A. `Cl - CH=CH_2`
B. `Cl–CH=CH–CH_3`
C. `Cl–CH=CH–OCH_3`
D. `Cl–CH=CH–NO_2`

Answer

To determine which compound has the shortest C–Cl bond length, we need to analyze the nature of the bonds in the given compounds. The bond length between carbon and chlorine depends on whether the bond is a single, double, or triple bond. Generally, the order of bond lengths from longest to shortest is as follows:

1. Single bond (C–Cl) - longest
2. Double bond (C=C) - shorter than single
3. Triple bond (C≡C) - shortest

Now, let's analyze the four compounds provided in the question step by step.

### Step 1: Identify the Compounds
Assume the compounds are:
- A: Cl–CH=CH2
- B: Cl–CH(CH3)–CH2
- C: Cl–CH=CH–OCH3
- D: Cl–CH=CH–NO2

### Step 2: Analyze Each Compound
1. **Compound A (Cl–CH=CH2)**:
- Contains a C=Cl bond. The presence of a double bond means that the bond length will be shorter than a single bond.

2. **Compound B (Cl–CH(CH3)–CH2)**:
- This compound has a single bond between C and Cl. Therefore, it will have a longer bond length compared to a double bond.

3. **Compound C (Cl–CH=CH–OCH3)**:
- Similar to compound A, it has a C=Cl bond. The presence of the double bond indicates a shorter bond length.

4. **Compound D (Cl–CH=CH–NO2)**:
- This compound also contains a C=Cl bond. The presence of the nitro group (NO2) can stabilize the double bond through resonance, which may lead to a shorter bond length.

### Step 3: Compare Stability and Bond Characteristics
- **Stability**: Among the compounds, the stability of the resonance structures affects the bond length. Compound D, with the nitro group, is likely to have a more stable resonance structure, leading to a stronger double bond character.
- **Bond Length**: Since compound D has the most stable resonance structure, it will exhibit a shorter C–Cl bond length compared to the other compounds.

### Conclusion
After analyzing the compounds and their bond characteristics, we conclude that **Compound D (Cl–CH=CH–NO2)** has the shortest C–Cl bond length due to the stability of its resonance structures and the presence of a double bond.