In which of the following does the first compound have a higher dipole moment than the second ?

Options

A.
B.
C.
D.

Explanation

To determine in which of the given pairs of compounds the first compound has a higher dipole moment than the second, we need to analyze the structures and the factors that influence dipole moments. The dipole moment (\( \mu \)) is defined as:

\[ \mu = Q \times D \]

where \( Q \) is the magnitude of the charge and \( D \) is the distance between the charges. Thus, the dipole moment is influenced by both the charge separation and the distance between the charges.

### Step-by-Step Solution:

1. **Analyze Option A:**
- The first compound has a resonance structure that allows for a significant charge separation (larger \( D \)).
- The second compound has a smaller charge separation.
- Since the distance \( D \) is larger in the first compound, the dipole moment of the first compound is higher than that of the second compound.
- **Conclusion:** Option A is correct.

2. **Analyze Option B:**
- The first compound has a resonance structure that results in a smaller charge separation compared to the second compound.
- The second compound has a pure single bond, which typically results in a smaller dipole moment.
- Since the distance \( D \) is smaller in the first compound, the dipole moment of the first compound is lower than that of the second compound.
- **Conclusion:** Option B is not correct.

3. **Analyze Option C:**
- The first compound has a charge separation that is less than that of the second compound.
- The resonance in the first compound leads to a decrease in the double bond character, which increases the bond length and thus reduces the dipole moment.
- The second compound has a more significant charge separation.
- **Conclusion:** Option C is not correct.

4. **Analyze Option D:**
- The first compound has resonance that increases the distance between the charges.
- The second compound has a smaller charge separation.
- Since the distance \( D \) is larger in the first compound, the dipole moment of the first compound is higher than that of the second compound.
- **Conclusion:** Option D is correct.

### Final Answer:
The correct options where the first compound has a higher dipole moment than the second are **A and D**.