Consider the following acids
1. `MeCH_(2)COOH`
2. `Me_(2)CHCOOH`
3. `Me_(3)C COOH`
4. `Et_(3)C COOH`
Correct order of the rate of esterification of these acids with `MeOH` is

Options

A. `1 gt 2 gt 3 gt 4`
B. `2 gt 1 gt 3 gt 4`
C. `2 gt 3 gt 4 gt 1`
D. `2 gt 3 gt 1 gt 4`

Answer

To determine the correct order of the rate of esterification of the given acids with methanol (MeOH), we need to analyze the structure of each acid and how the substituents affect the electrophilicity of the carbonyl carbon in the carboxylic acid group (-COOH). The rate of esterification is directly proportional to the electrophilicity of the carbonyl carbon, which means that a more electron-deficient carbonyl carbon will react faster with the alcohol.

### Step-by-Step Solution:

1. **Identify the Structures of the Acids**:
- 1. `MeCH2COOH` (Propanoic acid with a methyl group)
- 2. `Me2CHCOOH` (Butanoic acid with two methyl groups)
- 3. `Me3CCOOH` (Pentanoic acid with three methyl groups)
- 4. `Et3CCOOH` (Hexanoic acid with three ethyl groups)

2. **Analyze the Inductive Effect**:
- The presence of alkyl groups (methyl or ethyl) exerts a +I (inductive) effect, which increases the electron density on the carbonyl carbon. This reduces the electrophilicity of the carbonyl carbon, making it less reactive towards nucleophiles like methanol.

3. **Evaluate Each Acid**:
- **For `MeCH2COOH`**: There is one methyl group. The +I effect is minimal, leading to relatively high electrophilicity.
- **For `Me2CHCOOH`**: There are two methyl groups. The +I effect is greater than the first acid, decreasing electrophilicity further.
- **For `Me3CCOOH`**: There are three methyl groups. The +I effect is significant, leading to even lower electrophilicity.
- **For `Et3CCOOH`**: There are three ethyl groups. The +I effect is substantial, resulting in the lowest electrophilicity among the four acids.

4. **Determine the Rate of Esterification**:
- The acid with the highest electrophilicity will react the fastest with methanol. Therefore, the order from highest to lowest electrophilicity (and thus from fastest to slowest rate of esterification) is:
- `MeCH2COOH` > `Me2CHCOOH` > `Me3CCOOH` > `Et3CCOOH`

5. **Final Order of Esterification Rates**:
- The correct order of the rate of esterification of these acids with methanol is:
1. `MeCH2COOH`
2. `Me2CHCOOH`
3. `Me3CCOOH`
4. `Et3CCOOH`