Ionic species are stabilised by the dispersal of charge. Which of the following carboxylate ion is the most stable ?

Options

A. `CH_(3)-overset(O)overset(||)(C)-O^(-)`
B. `Cl-CH_(2)-overset(O)overset(||)(C)-O^(-)`
C. `F-CH_(2)-overset(O)overset(||)(C)-O^(-)`
D.

Explanation

To determine which carboxylate ion is the most stable, we need to consider the factors that stabilize the negative charge on the carboxylate ion. The stability of carboxylate ions is influenced by the ability of substituents to disperse the negative charge through inductive effects.

### Step-by-Step Solution:

1. **Identify the Carboxylate Ions**:
Let's consider the carboxylate ions that are being compared. For example, we can look at ions such as acetate (CH3COO⁻), chloroacetate (ClCH2COO⁻), and dichloroacetate (Cl2CHCOO⁻).

2. **Understand the Inductive Effect**:
The inductive effect is the electron-withdrawing or electron-donating effect of substituents through sigma bonds. Electron-withdrawing groups (EWGs) stabilize negative charges by pulling electron density away from the negatively charged site.

3. **Analyze the Substituents**:
- In acetate (CH3COO⁻), there are no strong electron-withdrawing groups.
- In chloroacetate (ClCH2COO⁻), the chlorine atom exerts a -I (negative inductive) effect, which helps stabilize the negative charge on the carboxylate ion.
- In dichloroacetate (Cl2CHCOO⁻), there are two chlorine atoms, which exert a stronger -I effect compared to one chlorine in chloroacetate.

4. **Compare the Stability**:
The more electron-withdrawing groups present, the greater the stabilization of the negative charge. Therefore:
- Acetate (CH3COO⁻) is the least stable due to the absence of electron-withdrawing groups.
- Chloroacetate (ClCH2COO⁻) is more stable than acetate due to the presence of one chlorine atom.
- Dichloroacetate (Cl2CHCOO⁻) is the most stable because it has two chlorine atoms that pull electron density away from the carboxylate ion, effectively stabilizing the negative charge.

5. **Conclusion**:
Based on the inductive effects of the substituents, the order of stability for the carboxylate ions is:
- Dichloroacetate (most stable) > Chloroacetate > Acetate (least stable).

### Final Answer:
The most stable carboxylate ion among the given options is **dichloroacetate (Cl2CHCOO⁻)**.