Among the following methyl halides the one with the highest value of dipole moment is :

Options

A. `CH_3F`
B. `CH_3CI`
C. `CH_3Br`
D. `CH_3I`

Answer

To determine which methyl halide has the highest dipole moment among CH3F, CH3Cl, CH3Br, and CH3I, we will analyze the electronegativity of the halogens and how it affects the dipole moment of each compound.

### Step-by-Step Solution:

1. **Understanding Dipole Moment**:
- The dipole moment (μ) is a measure of the separation of positive and negative charges in a molecule. It is influenced by the electronegativity of the atoms involved. The greater the difference in electronegativity between the bonded atoms, the higher the dipole moment.

2. **Electronegativity of Halogens**:
- The electronegativity values for the halogens are approximately:
- Fluorine (F): 4.0
- Chlorine (Cl): 3.0
- Bromine (Br): 2.8
- Iodine (I): 2.5
- As we move down the group in the periodic table, electronegativity decreases.

3. **Analyzing Each Methyl Halide**:
- **CH3F**: The dipole moment is influenced by the high electronegativity of fluorine (4.0).
- **CH3Cl**: Chlorine has a lower electronegativity (3.0) compared to fluorine, but due to its larger size, it can create a significant dipole moment.
- **CH3Br**: Bromine has an even lower electronegativity (2.8), leading to a smaller dipole moment than CH3Cl.
- **CH3I**: Iodine has the lowest electronegativity (2.5), resulting in the smallest dipole moment among the four.

4. **Comparing Dipole Moments**:
- Generally, the dipole moment is expected to decrease as we move from CH3F to CH3I due to decreasing electronegativity. However, CH3Cl exhibits an exception due to its size and the influence it has on the overall dipole moment.

5. **Conclusion**:
- After analyzing the electronegativities and the resulting dipole moments, we find that CH3Cl has the highest dipole moment among the given methyl halides.

### Final Answer:
**CH3Cl** has the highest value of dipole moment among the given methyl halides.