Which of the following presents the correct order of the acidity in the given compounds?

Options

A. `FCH_(2)COOH gt ClCH_(2)COOH gt BrCH_(2)COOH gt CH_(3)COOH`
B. `CH_(3)COOH gt BrCH_(2)COOHgtClCH_(2)COOH gt FCH_(2)COOH`
C. `FCH_(2)COOHgtCH_(3)COOH gt BrCH_(2)COOH gt ClCH_(2)COOH`
D. `BrCH_(2)COOH gt ClCH_(2)COOH gt FCH_(2)COOH gt CH_(3)COOH`

Answer

To determine the correct order of acidity among the given compounds (acetic acid, fluoroacetic acid, chloroacetic acid, and bromoacetic acid), we will analyze the stability of their conjugate bases. The acidity of a compound is influenced by the stability of the conjugate base formed after the removal of a proton (H⁺).

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have four compounds:
- Acetic Acid (CH₃COOH)
- Fluoroacetic Acid (FCH₂COOH)
- Chloroacetic Acid (ClCH₂COOH)
- Bromoacetic Acid (BrCH₂COOH)

2. **Form the Conjugate Bases**:
When each acid donates a proton (H⁺), it forms the following conjugate bases:
- Acetate Ion (CH₃COO⁻)
- Fluoroacetate Ion (FCH₂COO⁻)
- Chloroacetate Ion (ClCH₂COO⁻)
- Bromoacetate Ion (BrCH₂COO⁻)

3. **Analyze the Effects of Halogens**:
The halogens (F, Cl, Br) are electronegative and exhibit a -I (inductive) effect, which stabilizes the negative charge on the conjugate base. The strength of this inductive effect depends on the electronegativity of the halogen:
- Fluorine (F) has the highest electronegativity, followed by chlorine (Cl), and then bromine (Br).

4. **Stability of Conjugate Bases**:
- **Fluoroacetate Ion (FCH₂COO⁻)**: The presence of fluorine stabilizes the negative charge the most due to its high electronegativity.
- **Chloroacetate Ion (ClCH₂COO⁻)**: Chlorine is less electronegative than fluorine, so it provides less stabilization than fluoroacetate.
- **Bromoacetate Ion (BrCH₂COO⁻)**: Bromine is the least electronegative among the three halogens, providing the least stabilization.
- **Acetate Ion (CH₃COO⁻)**: The acetate ion does not have any halogen to stabilize the negative charge, making it less stable compared to the halogenated derivatives.

5. **Order of Acidity**:
Based on the stability of the conjugate bases, we can establish the order of acidity:
- **Fluoroacetic Acid > Chloroacetic Acid > Bromoacetic Acid > Acetic Acid**

### Final Order of Acidity:
Fluoroacetic Acid > Chloroacetic Acid > Bromoacetic Acid > Acetic Acid