In which of the following cases dipole moment will be highest ?

Options

A. `CH_(3)-CF_(3)`
B. `FCH_(2)-CH_(2)F`
C. `F_(2)C = CF_(2)`
D. `CF_(3) - CF_(3)`

Answer

To determine which of the given cases has the highest dipole moment, we need to analyze the molecular structures and the electronegativities of the atoms involved. Here’s a step-by-step solution:

### Step 1: Understand Dipole Moment
The dipole moment (\( \mu \)) is a measure of the separation of positive and negative charges in a molecule. It is a vector quantity, directed from the positive charge to the negative charge. The dipole moment can be calculated using the formula:
\[ \mu = q \times d \]
where \( q \) is the charge and \( d \) is the distance between the charges.

### Step 2: Analyze Each Case
1. **Case 1: CH3 (Methyl group)**
- The methyl group has three hydrogen atoms attached to a carbon atom. The electronegativity difference between carbon and hydrogen is not significant enough to create a strong dipole moment. Thus, the dipole moment is low.

2. **Case 2: CF3 (Trifluoromethyl group)**
- The trifluoromethyl group has three fluorine atoms attached to a carbon atom. Fluorine is highly electronegative, creating a strong dipole moment directed towards the fluorine atoms. However, due to symmetry, the dipole moments from the three C-F bonds will cancel out, resulting in a net dipole moment of zero.

3. **Case 3: CH2F2 (Difluoromethane)**
- In difluoromethane, there are two fluorine atoms and two hydrogen atoms attached to a carbon atom. The dipole moments from the C-F bonds will not cancel out completely due to the asymmetrical arrangement of the atoms, leading to a net dipole moment.

4. **Case 4: CF2H2 (Fluoromethane)**
- Similar to CH2F2, this molecule has two fluorine atoms and two hydrogen atoms. The dipole moments will also not cancel out due to the asymmetrical arrangement, resulting in a net dipole moment.

### Step 3: Compare Dipole Moments
- **CH3**: Low dipole moment (nearly zero).
- **CF3**: Dipole moment is zero due to symmetry.
- **CH2F2**: Has a net dipole moment due to asymmetry.
- **CF2H2**: Also has a net dipole moment due to asymmetry.

### Conclusion
Among the given cases, **CH2F2** and **CF2H2** will have dipole moments, but CH2F2 is expected to have a higher dipole moment due to the presence of two highly electronegative fluorine atoms and the arrangement of hydrogen atoms. Therefore, the case with the highest dipole moment is **CH2F2**.

### Final Answer
The dipole moment will be highest in **CH2F2**.

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