Among the given pairs, in which pair second compound has less enol content:

Options

A.
B.
C.
D.

Answer

To determine which pair of compounds has the second compound with less enol content, we need to analyze the structures of the compounds in each pair. Enol content refers to the presence of enol forms (alkenes with an -OH group) in comparison to their keto forms (carbonyl compounds). The stability of these forms can vary based on the structure of the compounds.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- We have four pairs of compounds to analyze. Each pair consists of a first compound and a second compound.

2. **Analyze the First Pair:**
- **First Compound:** Aliphatic compound with a double bond and a hydroxyl group (OH).
- **Second Compound:** Aromatic compound with a similar structure.
- **Conclusion:** The aromatic compound generally has more enol content due to resonance stabilization. Thus, the second compound has more enol content than the first.

3. **Analyze the Second Pair:**
- **First Compound:** Aromatic compound with a double bond and an OH group.
- **Second Compound:** Another aromatic compound with a similar structure.
- **Conclusion:** Both compounds are aromatic, but the second compound has more double bonds, leading to higher enol content compared to the first compound.

4. **Analyze the Third Pair:**
- **First Compound:** Two aromatic rings with a double bond and an OH group.
- **Second Compound:** Similar structure but with a different arrangement.
- **Conclusion:** The first compound is more stable and has more enol content than the second compound.

5. **Analyze the Fourth Pair:**
- **First Compound:** Two aromatic rings with a double bond and an OH group.
- **Second Compound:** Similar structure.
- **Conclusion:** The first compound is more stable and has more enol content than the second compound.

6. **Final Decision:**
- From the analysis, the pairs where the second compound has less enol content than the first are:
- Pair 3 (first compound has more enol content)
- Pair 4 (first compound has more enol content)

### Summary of Findings:
- The pairs where the second compound has less enol content than the first are the third and fourth pairs.