Which of the following compounds is the most acidic ?

Options

A. `HCO_(2)H`
B. `CH_(3)CO_(2)H`
C. `CH_(3)CH_(2)CO_(2)H`
D. `"CC"l_(3)CO_(2)H`

Answer

To determine which of the given compounds is the most acidic, we need to analyze the effects of the substituents on the carboxylic acid group (–COOH) in each compound. The acidity of carboxylic acids is influenced by the nature of the substituents attached to the carbon chain, particularly their electron-withdrawing or electron-donating effects.

### Step-by-Step Solution:

1. **Identify the Compounds**:
Let's assume the compounds are as follows:
- A: HCOOH (formic acid)
- B: CH3COOH (acetic acid)
- C: CH3CH2COOH (propanoic acid)
- D: CCl3COOH (trichloroacetic acid)

2. **Understand Acidic Strength**:
The acidic strength of carboxylic acids is affected by the stability of their conjugate bases. A more stable conjugate base corresponds to a stronger acid.
- Electron-withdrawing groups (EWGs) stabilize the conjugate base by delocalizing negative charge.
- Electron-donating groups (EDGs) destabilize the conjugate base.

3. **Analyze Each Compound**:
- **Compound A (HCOOH)**: The hydrogen atom does not have a significant electron-withdrawing or donating effect. It is a weak acid.
- **Compound B (CH3COOH)**: The methyl group (–CH3) is an electron-donating group (+I effect), which decreases acidity compared to formic acid.
- **Compound C (CH3CH2COOH)**: The ethyl group (–C2H5) also has a +I effect, further decreasing acidity compared to acetic acid.
- **Compound D (CCl3COOH)**: The trichloro group (–CCl3) is a strong electron-withdrawing group (–I effect), which stabilizes the conjugate base significantly, making this compound a strong acid.

4. **Determine the Most Acidic Compound**:
Based on the analysis:
- Compound D (CCl3COOH) has the strongest acidic character due to the presence of the electron-withdrawing trichloro group, which stabilizes the conjugate base effectively.

### Conclusion:
The most acidic compound among the given options is **CCl3COOH (trichloroacetic acid)**.

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