Which of the following represents the correct order of the acidic strength in the given compounds ?

Options

A. (a) `FCH_2COOH gt CH_3COOH gt BrCH_3COOH gt ClCH_2COOH`
B. (b) `BrCH_2COOH gt ClCH_2COOH gt FCH_2COOH gt CH_3COOH`
C. (c) `FCH_2COOH gt ClCH_2COOH gt BrCH_2COOH gt CH_3COOH`
D. (d) `CH_3COOH gt BrCH_2COOH gt ClCH_2COOH lt FCH_2COOH`

Explanation

To determine the correct order of acidic strength among the given compounds: fluoroacetic acid (FCH2COOH), chloroacetic acid (ClCH2COOH), bromoacetic acid (BrCH2COOH), and acetic acid (CH3COOH), we can follow these steps:

### Step 1: Understand the Role of Electron Withdrawing Groups
- Electron withdrawing groups (EWGs) increase the acidity of carboxylic acids by stabilizing the negative charge on the carboxylate ion formed after deprotonation. The more effective the EWG, the stronger the acid.

### Step 2: Identify the Electronegative Atoms
- The compounds contain halogens (F, Cl, Br) as electron withdrawing groups. The order of electronegativity among these halogens is:
- Fluorine (F) > Chlorine (Cl) > Bromine (Br)

### Step 3: Analyze the Inductive Effect
- The inductive effect (−I effect) is the ability of an atom to attract electrons towards itself. The stronger the −I effect, the more acidic the compound:
- Fluoroacetic acid (FCH2COOH) will have the strongest −I effect due to fluorine.
- Chloroacetic acid (ClCH2COOH) will have a moderate −I effect due to chlorine.
- Bromoacetic acid (BrCH2COOH) will have the weakest −I effect among the halogens.
- Acetic acid (CH3COOH) has no electron withdrawing group and will be the least acidic.

### Step 4: Establish the Order of Acidity
- Based on the −I effect:
1. Fluoroacetic acid (FCH2COOH) - strongest acid
2. Chloroacetic acid (ClCH2COOH)
3. Bromoacetic acid (BrCH2COOH)
4. Acetic acid (CH3COOH) - weakest acid

### Final Order of Acidity
Thus, the correct order of acidic strength is:
**Fluoroacetic acid > Chloroacetic acid > Bromoacetic acid > Acetic acid**

### Conclusion
The correct answer is given in option C.

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