The correct order of decreasing acidity of nitrophenols will be

Options

A. m-nitrophenolgtp-nitrophenolgto-nitrophenol
B. o-nitrophenolgtm-nitrophenolgtp-nitrophenol
C. p-nitrophenolgtm-nitrophenolgto-nitrophenol
D. p-nitrophenolgto-nitrophenol-m-nitrophenol

Explanation

To determine the correct order of decreasing acidity of nitrophenols (ortho-nitrophenol, meta-nitrophenol, and para-nitrophenol), we can follow these steps:

### Step 1: Understand the Structure of Nitrophenols
- **Ortho-nitrophenol** has the nitro group (-NO2) at the 2-position.
- **Meta-nitrophenol** has the nitro group at the 3-position.
- **Para-nitrophenol** has the nitro group at the 4-position.

### Step 2: Identify the Effects of the Nitro Group
- The nitro group is a strong electron-withdrawing group due to its -M (mesomeric) and -I (inductive) effects.
- In ortho and para positions, the nitro group can stabilize the negative charge of the conjugate base through resonance (due to -M effect).
- In the meta position, the nitro group cannot stabilize the negative charge through resonance, only through inductive effect (-I).

### Step 3: Analyze the Stability of Conjugate Bases
- When nitrophenols lose a proton (H+), they form a conjugate base.
- The stability of the conjugate base is crucial for acidity: more stable conjugate bases correspond to stronger acids.
- For ortho and para-nitrophenols, the conjugate bases can delocalize the negative charge due to resonance with the nitro group.
- For meta-nitrophenol, the negative charge cannot be delocalized effectively, making it less stable.

### Step 4: Consider Hydrogen Bonding
- In ortho-nitrophenol, there is potential for intramolecular hydrogen bonding before the proton is lost, which can hinder the release of H+ and thus reduce acidity.
- Para-nitrophenol does not have this issue and can release H+ more easily, making it a stronger acid than ortho-nitrophenol.

### Step 5: Establish the Order of Acidity
- Based on the above analysis:
- **Para-nitrophenol** is the most acidic due to effective resonance stabilization of the conjugate base and lack of hydrogen bonding issues.
- **Ortho-nitrophenol** is next, as it has resonance stabilization but is somewhat hindered by hydrogen bonding.
- **Meta-nitrophenol** is the least acidic because it only has inductive stabilization and lacks resonance stabilization.

### Final Order of Decreasing Acidity
- The correct order of decreasing acidity of nitrophenols is:
**Para-nitrophenol > Ortho-nitrophenol > Meta-nitrophenol**

---