Which of the following has highest tendency to ionise in aqueous solution ?

Options

A. HCOOH
B. `CH_(3)COOH`
C. `FCH_(2)COOH`
D. `BrCH_(2)COOH`

Answer

To determine which of the given compounds has the highest tendency to ionize in aqueous solution, we need to analyze the structures and the influence of substituents on their ionization.

### Step 1: Identify the Compounds
The compounds given are:
1. HCOOH (Formic acid)
2. CH3COOH (Acetic acid)
3. FCH2COOH (Fluoroacetic acid)
4. BrCH2COOH (Bromoacetic acid)

### Step 2: Understand Ionization
Ionization in aqueous solution refers to the process where a compound dissociates into ions. For carboxylic acids, this typically involves the release of a proton (H+) from the carboxyl group (-COOH).

### Step 3: Analyze the Effect of Substituents
The presence of electronegative atoms (like halogens) near the carboxylic acid group can significantly affect its acidity and tendency to ionize. Electronegative atoms stabilize the negative charge on the conjugate base formed after ionization, thus promoting ionization.

### Step 4: Compare the Compounds
- **HCOOH (Formic acid)**: No electronegative substituents, moderate tendency to ionize.
- **CH3COOH (Acetic acid)**: Methyl group is weakly electron-donating, reducing ionization tendency compared to formic acid.
- **FCH2COOH (Fluoroacetic acid)**: The fluorine atom is highly electronegative, which will stabilize the conjugate base (FCH2COO-) and increase the tendency to ionize.
- **BrCH2COOH (Bromoacetic acid)**: Bromine is less electronegative than fluorine, so it will stabilize the conjugate base less effectively than fluorine.

### Step 5: Conclusion
Among the given compounds, **FCH2COOH (Fluoroacetic acid)** has the highest tendency to ionize in aqueous solution due to the strong electronegative effect of fluorine, which enhances the stability of the conjugate base.

### Final Answer
The compound with the highest tendency to ionize in aqueous solution is **FCH2COOH**.

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