In which of the following lone-pair indicated is involved in resonance:

Options

A.
B.
C.
D.

Explanation

To determine which lone pairs are involved in resonance among the given compounds, we will analyze each structure step by step.

### Step 1: Analyze the first compound
- **Structure**: Identify the presence of a nitrogen atom with a lone pair and a double bond.
- **Observation**: The lone pair is localized next to the double bond.
- **Conclusion**: Since the lone pair is localized and does not have the ability to delocalize over adjacent π bonds, it does not participate in resonance.

**Hint**: Look for lone pairs adjacent to double or triple bonds; if they are localized, they do not participate in resonance.

### Step 2: Analyze the second compound
- **Structure**: Examine the structure for a lone pair that is adjacent to a double bond.
- **Observation**: The lone pair can overlap with the π bond of the double bond.
- **Conclusion**: This lone pair is delocalized and can participate in resonance.

**Hint**: If a lone pair can overlap with a π bond, it is likely to participate in resonance.

### Step 3: Analyze the third compound
- **Structure**: Look for a lone pair that is part of a conjugated system (alternating single and double bonds).
- **Observation**: The lone pair can be delocalized across the conjugated system.
- **Conclusion**: This lone pair is also involved in resonance due to its ability to participate in the delocalization.

**Hint**: Conjugated systems allow lone pairs to participate in resonance; check for alternating double bonds.

### Final Conclusion
After analyzing all the compounds:
- The lone pairs in the **second** and **third** compounds participate in resonance.
- The lone pair in the **first** compound does not participate in resonance.

**Correct Options**: Second and Third compounds.