Consider the following compounds
`O_(2)N-CH_(2)-underset((I))overset(O)overset(||)C-OH" "F-CH_(2)-underset((II))overset(O)overset(||)C-OH" "Ph-CH_(2)-underset((III))overset(O)overset(||)C-OH" "CH_(3)-underset((IV))(CH_(2))-overset(O)overset(||)C-OH`
Which statement is/are correct :

Options

A. `I gt II gt III gt IV` (Acidic strength order)
B. I is most acidic because of -M effect of `-NO_(2)` group
C. I is most acidic because of -I effect of `-NO_(2)` group
D. IV is least acidic because of `+I` Effect.

Answer

To determine the correct statements regarding the acidic strength of the given compounds, let's analyze each compound step by step.

### Step 1: Identify the compounds
The compounds given are:
1. **Compound I:** O₂N-CH₂-C(=O)-OH (Nitro group)
2. **Compound II:** F-CH₂-C(=O)-OH (Fluoro group)
3. **Compound III:** Ph-CH₂-C(=O)-OH (Phenyl group)
4. **Compound IV:** CH₃-CH₂-C(=O)-OH (Methyl group)

### Step 2: Analyze the effects of substituents
- **Compound I (NO₂):** The nitro group (NO₂) is a strong electron-withdrawing group due to its -I (inductive) and -M (mesomeric) effects. This stabilizes the negative charge on the oxygen atom after the release of H⁺, making it highly acidic.

- **Compound II (F):** The fluorine atom (F) also exhibits a -I effect, which stabilizes the negative charge, but it is less effective than the nitro group. Therefore, it is less acidic than Compound I.

- **Compound III (Ph):** The phenyl group (Ph) has a -I effect but is less effective than both NO₂ and F. Thus, it is less acidic than Compound II.

- **Compound IV (CH₃):** The methyl group (CH₃) has a +I effect, which destabilizes the negative charge on the oxygen after H⁺ release, making it the least acidic among the four compounds.

### Step 3: Establish the order of acidity
Based on the analysis:
- Compound I (NO₂) is the most acidic.
- Compound II (F) is next.
- Compound III (Ph) follows.
- Compound IV (CH₃) is the least acidic.

The order of acidity is:
**I > II > III > IV**

### Step 4: Evaluate the statements
1. **Statement 1:** "1 > 2 > 3 > 4" - **Correct** (as derived from the analysis).
2. **Statement 2:** "The first structure is most acidic because of the -M effect of NO₂ group" - **Correct** (NO₂ has both -I and -M effects contributing to acidity).
3. **Statement 3:** "The third structure is most acidic because of the -I effect of NO₂ group" - **Incorrect** (the third structure is not the most acidic; it is the first structure).
4. **Statement 4:** "IV is least acidic because of +I effect" - **Correct** (the +I effect of CH₃ destabilizes the negative charge).

### Conclusion
The correct statements are:
- Statement 1
- Statement 2
- Statement 4