Which one of the following is the correct order of acidic strength?
(i) `Cl_(3)C-COOH`
(ii) `Cl_(2)CH-COOH`
(iii) `ClCH_(2)-COOH`
(iv) `CH_(3)-COOH`

Options

A. `iv gt iii gt ii gt i`
B. `igt ii gt iii gt iv`
C. `igt iii gt ii gt iv`
D. `iv gt ii gt iii gt i`

Answer

To determine the correct order of acidic strength for the given compounds, we need to analyze the effect of substituents on the carboxylic acid group (-COOH) in each compound. The compounds are:

1. \( \text{Cl}_3\text{C-COOH} \) (Compound 1)
2. \( \text{Cl}_2\text{CH-COOH} \) (Compound 2)
3. \( \text{ClCH}_2\text{COOH} \) (Compound 3)
4. \( \text{CH}_3\text{COOH} \) (Compound 4)

### Step 1: Analyze Compound 1 (\( \text{Cl}_3\text{C-COOH} \))
- This compound has three chlorine atoms attached to the carbon adjacent to the carboxylic acid group.
- Chlorine is an electron-withdrawing group due to its electronegativity (−I effect).
- The presence of three chlorine atoms increases the electron deficiency at the carboxylic acid hydrogen, making it easier to lose the hydrogen ion (H⁺).
- Therefore, this compound has the highest acidic strength.

### Step 2: Analyze Compound 2 (\( \text{Cl}_2\text{CH-COOH} \))
- This compound has two chlorine atoms attached to the carbon adjacent to the carboxylic acid group.
- Similar to Compound 1, the chlorine atoms withdraw electron density from the carboxylic acid group, but there are fewer chlorine atoms.
- Thus, it is less acidic than Compound 1 but more acidic than the following compounds.

### Step 3: Analyze Compound 3 (\( \text{ClCH}_2\text{COOH} \))
- This compound has one chlorine atom attached to the carbon adjacent to the carboxylic acid group.
- With only one electron-withdrawing chlorine atom, the acidic strength is further reduced compared to Compounds 1 and 2.
- Therefore, it is less acidic than both Compound 1 and Compound 2.

### Step 4: Analyze Compound 4 (\( \text{CH}_3\text{COOH} \))
- This compound has a methyl group (−CH₃) attached to the carbon adjacent to the carboxylic acid group.
- The methyl group is an electron-donating group (+I effect), which increases electron density at the carboxylic acid hydrogen.
- As a result, it makes it more difficult for the hydrogen to dissociate, leading to the lowest acidic strength among all the compounds.

### Conclusion: Order of Acidic Strength
Based on the analysis, the order of acidic strength from strongest to weakest is:
1. \( \text{Cl}_3\text{C-COOH} \) (Compound 1)
2. \( \text{Cl}_2\text{CH-COOH} \) (Compound 2)
3. \( \text{ClCH}_2\text{COOH} \) (Compound 3)
4. \( \text{CH}_3\text{COOH} \) (Compound 4)

Thus, the correct order of acidic strength is:
\[ \text{Cl}_3\text{C-COOH} > \text{Cl}_2\text{CH-COOH} > \text{ClCH}_2\text{COOH} > \text{CH}_3\text{COOH} \]