Which of the following carboxylic acids is the most reactive towards esterification ?

Options

A. `(CH_3)_3"CCOOH"`
B. `(CH_3)_2CHCOOH`
C. `CH_3CH_2COOH`
D. `(C_2H_5)_2CHCOOH`

Answer

To determine which carboxylic acid is the most reactive towards esterification, we need to analyze the given compounds based on their structure and the presence of electron-donating groups.

### Step-by-Step Solution:

1. **Understanding Esterification**: Esterification is a reaction between a carboxylic acid and an alcohol, typically in the presence of a strong acid catalyst (like concentrated H2SO4), resulting in the formation of an ester and water.

2. **Identifying the Compounds**: The question presents four carboxylic acids:
- Compound 1: CH3C(=O)OH (trifluoroacetic acid)
- Compound 2: CH3CH(=O)OH (isobutyric acid)
- Compound 3: CH3CH2C(=O)OH (butyric acid)
- Compound 4: CH3C(=O)OH (acetic acid)

3. **Analyzing Electron-Releasing Groups**: The reactivity of carboxylic acids in esterification is influenced by the presence of electron-releasing groups (alkyl groups). More electron-releasing groups can stabilize the carboxylate ion formed during the reaction, making the acid less reactive.

4. **Counting Electron-Releasing Groups**:
- Compound 1 (trifluoroacetic acid): No electron-releasing groups.
- Compound 2 (isobutyric acid): One electron-releasing group (CH3).
- Compound 3 (butyric acid): Two electron-releasing groups (CH3 and CH2).
- Compound 4 (acetic acid): One electron-releasing group (CH3).

5. **Determining Reactivity**: The compound with the least number of electron-releasing groups will be the most reactive towards esterification. Therefore:
- Compound 1 is the least reactive due to the absence of electron-releasing groups.
- Compound 2 and Compound 4 have one electron-releasing group.
- Compound 3 has two electron-releasing groups, making it the most reactive.

6. **Conclusion**: Based on the analysis, Compound 3 (butyric acid, CH3CH2C(=O)OH) is the most reactive towards esterification.

### Final Answer:
The most reactive carboxylic acid towards esterification is **Compound 3: CH3CH2COOH (butyric acid)**.