Consider the following haloalkanes,
I. `CH_(3)l` II. `CH_(3)F`
III. `CH_(3)Cl` IV. `CH_(3)Br`
The correct sequence of increasing order of dipole moment is

Options

A. `Ilt II ltIII lt IV`
B. `IV lt III lt II lt I`
C. `I lt IV lt II lt III`
D. `III lt IV lt I lt II`

Explanation

To determine the correct sequence of increasing order of dipole moment for the given haloalkanes, we will analyze each compound based on the electronegativity of the halogen atoms and the bond lengths.

### Step-by-Step Solution:

1. **Identify the Compounds**: The haloalkanes given are:
- I. `CH₃I` (Methyl iodide)
- II. `CH₃F` (Methyl fluoride)
- III. `CH₃Cl` (Methyl chloride)
- IV. `CH₃Br` (Methyl bromide)

2. **Understand Dipole Moment**: The dipole moment (μ) is given by the formula:
\[ μ = q \times r \]
where \( q \) is the charge separation and \( r \) is the distance between the charges. A larger charge separation and a longer bond length will increase the dipole moment.

3. **Electronegativity of Halogens**: The electronegativity of the halogens (from highest to lowest) is:
- Fluorine (F) > Chlorine (Cl) > Bromine (Br) > Iodine (I)

4. **Bond Lengths**: The bond lengths (from shortest to longest) are generally:
- C-F < C-Cl < C-Br < C-I

5. **Analyzing Each Compound**:
- **`CH₃F`**: Strong electronegativity (highest) and short bond length → High dipole moment.
- **`CH₃Cl`**: Moderate electronegativity and moderate bond length → Moderate dipole moment.
- **`CH₃Br`**: Lower electronegativity and longer bond length → Lower dipole moment than `CH₃Cl`.
- **`CH₃I`**: Lowest electronegativity and longest bond length → Lowest dipole moment.

6. **Order of Dipole Moments**: Based on the analysis:
- `CH₃I` has the lowest dipole moment.
- `CH₃Br` has a higher dipole moment than `CH₃I`.
- `CH₃Cl` has a higher dipole moment than `CH₃Br`.
- `CH₃F` has the highest dipole moment.

7. **Final Sequence**: The correct sequence of increasing order of dipole moment is:
\[ CH₃I < CH₃Br < CH₃Cl < CH₃F \]

### Conclusion:
The correct answer is:
- **`CH₃I < CH₃Br < CH₃Cl < CH₃F`**