Which of the following is the strongest `-I` group :

Options

A. `-overset(+)N(CH_(3))_(3)`
B. `-overset(+)NH_(3)`
C. `-overset(+)S(CH_(3))_(2)`
D. `-F`

Answer

To determine which of the following is the strongest -I group, we need to understand the concept of the inductive effect, particularly the -I (minus I) effect. The -I effect refers to the ability of an electronegative atom or group to withdraw electron density from a sigma bond, resulting in polarization of that bond.

### Step-by-Step Solution:

1. **Understand the Inductive Effect**:
- The inductive effect is the polarization of sigma bonds due to the electronegativity of atoms or groups attached to the carbon chain. There are two types: +I (electron-donating) and -I (electron-withdrawing).

2. **Identify the Groups**:
- The question provides several groups or atoms. For this example, let's consider nitrogen (N), sulfur (S), and fluorine (F).

3. **Evaluate Electronegativity**:
- The strength of the -I effect is influenced by the electronegativity of the atoms. The more electronegative an atom is, the stronger its -I effect will be.
- Electronegativity values (Pauling scale):
- Fluorine (F) > Nitrogen (N) > Sulfur (S)

4. **Consider the Presence of Positive Charge**:
- If an electronegative atom carries a positive charge, it becomes unstable and will tend to withdraw electrons more strongly to stabilize itself.
- For example, if nitrogen or sulfur has a positive charge, it will exhibit a stronger -I effect than when they are neutral.

5. **Compare the Groups**:
- Fluorine is highly electronegative but may not be the strongest -I group if it is neutral.
- Nitrogen, when positively charged, will have a strong -I effect due to its electronegativity and instability.
- Sulfur, while electronegative, is less so than nitrogen.

6. **Conclusion**:
- Based on electronegativity and the effect of positive charge, nitrogen (especially when positively charged) will exhibit the strongest -I effect, followed by sulfur and then fluorine.

### Final Answer:
The strongest -I group among the given options is nitrogen (N).