The decreasing order of nucleophilicities in `DMSO` (dimethylsulphoxide) is :

Options

A. `F^(Ө) gt Cl^(Ө) gt Br^(Ө) gt I^(Ө)`
B. `I^(Ө) gt Br^(Ө) gt Cl^(Ө) gt F^(Ө)`
C. `F^(Ө) gt Cl^(Ө) gt I^(Ө) gt Br^(Ө)`
D. `I^(Ө) gt Br^(Ө) gt F^(Ө) gt Cl^(Ө)`

Answer

To determine the decreasing order of nucleophilicities in DMSO (dimethylsulfoxide), we need to analyze the behavior of different nucleophiles in this polar aprotic solvent.

### Step-by-Step Solution:

1. **Understanding DMSO**:
- DMSO is a polar aprotic solvent, which means it can solvate cations but does not effectively solvate anions. This property allows anions to remain relatively free and reactive.

2. **Nucleophilicity and Basicity**:
- In DMSO, the nucleophilicity of anions is directly related to their basicity. The more basic an anion is, the more nucleophilic it will be in this solvent.

3. **Analyzing Halide Ions**:
- We will compare the nucleophilicity of halide ions: fluoride (F⁻), chloride (Cl⁻), bromide (Br⁻), and iodide (I⁻).
- As we move down the group in the periodic table from fluoride to iodide, the basicity decreases due to the increasing size and decreasing electronegativity of the halide ions.

4. **Order of Basicity**:
- The order of basicity (and thus nucleophilicity in DMSO) for halides is:
- F⁻ > Cl⁻ > Br⁻ > I⁻
- Fluoride is the most basic and nucleophilic, while iodide is the least.

5. **Conclusion**:
- Therefore, the decreasing order of nucleophilicities in DMSO is:
- F⁻ > Cl⁻ > Br⁻ > I⁻

### Final Answer:
The decreasing order of nucleophilicities in DMSO is: **F⁻ > Cl⁻ > Br⁻ > I⁻**