The strongest acid amongst the following compounds is?

Options

A. 1)`CH_(3)CH_(2)CH(Cl)CO_(2)H`
B. 2)`ClCH_(2)CH_(2)CH_(2)COOH`
C. 3) `CH_(3)COOH`
D. 4) `HCOOH`

Answer

To determine the strongest acid among the given compounds, we will analyze the acidic strength of each compound based on the presence of electron-withdrawing and electron-donating groups.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have four carboxylic acids to compare. Let's denote them as A, B, C, and D.

2. **Understand Acidic Strength**:
The acidic strength of carboxylic acids is influenced by the presence of substituents. Electron-withdrawing groups (EWGs) increase acidity by stabilizing the negative charge on the conjugate base. Conversely, electron-donating groups (EDGs) decrease acidity.

3. **Identify Electron-Withdrawing and Electron-Donating Groups**:
- **Electron-Withdrawing Groups (EWGs)**: These include groups like -NO2, -Cl, -Br, etc., which exhibit a -I (inductive) effect and/or a -M (mesomeric) effect.
- **Electron-Donating Groups (EDGs)**: These include alkyl groups (like -CH3, -C2H5), which exhibit a +I (inductive) effect and/or a +M (mesomeric) effect.

4. **Evaluate Each Compound**:
- **Compound A**: Contains a chlorine atom at the alpha position (closest to the carboxylic group). Chlorine is an EWG and will significantly enhance the acidity.
- **Compound B**: Contains a chlorine atom at the gamma position (further from the carboxylic group). The effect of chlorine is less pronounced here.
- **Compound C**: Contains a methyl group (EDG), which will decrease acidity.
- **Compound D**: Contains no substituents, so it will have a baseline acidity.

5. **Compare the Effects**:
- The compound with the chlorine at the alpha position (Compound A) will have the strongest acidic strength due to the proximity of the EWG, which stabilizes the negative charge on the conjugate base effectively.
- Compound B, while it has a chlorine, is less acidic due to its position.
- Compounds C and D will be the least acidic due to the presence of EDGs or lack of substituents.

6. **Conclusion**:
Based on the analysis, Compound A (2-chlorobutanoic acid) is the strongest acid among the given compounds.

### Final Answer:
The strongest acid among the following compounds is **2-chlorobutanoic acid (Compound A)**.

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