Which of the following is correct order of order of dipole moment :-

Options

A. `CH_(3)-FgtCH_(3)-ClgtCH_(3)-BrgtCH_(3)-I`
B. `CH_(3)-ClgtCH_(3)-FgtCH_(3)-BrgtCH_(3)-I`
C. `CH_(3)-ClgtCH_(2)Cl_(2)gtC Cl_(4)gtCHCl_(3)`
D. `CH_(2)Cl_(2)gtCH_(3)ClgtCHCl_(3)gtC Cl_(4)`

Answer

To determine the correct order of dipole moments for the given compounds, we need to consider two main factors: the electronegativity of the atoms involved and the molecular geometry. Let's analyze the compounds step by step.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have the following compounds to analyze:
- CH3F (methyl fluoride)
- CH3Cl (methyl chloride)
- CH3Br (methyl bromide)
- CH3I (methyl iodide)

2. **Understand Electronegativity**:
The dipole moment (μ) is influenced by the difference in electronegativity between the bonded atoms. In this case, we have carbon (C) bonded to halogens (F, Cl, Br, I). The electronegativity values are approximately:
- F > Cl > Br > I

3. **Evaluate the Size of Halogens**:
As we move down the group in the periodic table from F to I, the size of the halogen atoms increases. This increase in size leads to a decrease in the bond polarity because the charge distribution becomes less effective due to the larger atomic radius.

4. **Determine the Order of Dipole Moments**:
- **CH3F**: Highest dipole moment due to the highest electronegativity of fluorine.
- **CH3Cl**: Lower than CH3F but higher than CH3Br due to chlorine's electronegativity.
- **CH3Br**: Lower than CH3Cl due to bromine's lower electronegativity.
- **CH3I**: Lowest dipole moment because iodine has the lowest electronegativity and the largest size.

Therefore, the order of dipole moments based on the above reasoning is:
\[ \text{CH3F} > \text{CH3Cl} > \text{CH3Br} > \text{CH3I} \]

5. **Consider Additional Compounds**:
Now, let's analyze the second set of compounds:
- CH2Cl2 (dichloromethane)
- CCl4 (carbon tetrachloride)
- CHCl3 (chloroform)
- CH3Cl (methyl chloride)

In this case, we need to consider the number of chlorine atoms and their arrangement:
- **CH3Cl**: Has one chlorine and is polar.
- **CH2Cl2**: Has two chlorines, which increases the dipole moment due to the vector addition of dipole moments.
- **CHCl3**: Has three chlorines, which also contributes to a significant dipole moment.
- **CCl4**: Is non-polar because the dipole moments cancel out due to symmetrical arrangement.

The order of dipole moments for these compounds is:
\[ \text{CHCl3} > \text{CH2Cl2} > \text{CH3Cl} > \text{CCl4} \]

### Final Conclusion:
Combining both analyses, the correct order of dipole moments is:
\[ \text{CH3F} > \text{CH3Cl} > \text{CH3Br} > \text{CH3I} \quad \text{and} \quad \text{CHCl3} > \text{CH2Cl2} > \text{CH3Cl} > \text{CCl4} \]