The origin of acidity and basicity in organic compound is great interest and provides an extensive comparison. Among hydrocarbons `%` a character is taken in aC Count while to decide the acidity, in simple aliphatic acids, more the number of alkyl groups, (+1 effect) less is the acidity `&` more the (-1 effect) groups larger the acidity and vice-versa in the case of simple alphatic bases. Benzoic acid is more stronger than carboxylic acid as benzoate ion is stablised more by resonance. Aromatic amines are less basic than apiphatic amine as the electron pair is less available in case of aromatic amines. The presence of solvent also plays a very important role and at time governs the order too.
Which of the following orders regarding acid strength is correct ?

Options

A. `HCOOHltCH_(3)COOHltPhCOOH`
B. `HCOOHgtPhCOOHgtCH_(3)COOH`
C. `HCOOHgtCH_(3)COOHgtPhCOOH`
D. `CH_(3)COOHgtHCOOHgtPhCOOH`

Answer

To determine the correct order of acid strength among the given acids, we need to analyze the stability of their conjugate bases. The stability of the conjugate base directly influences the acidity of the acid itself. Here’s a step-by-step solution:

### Step 1: Identify the Acids and Their Conjugate Bases
1. **Formic Acid (HCOOH)**: The conjugate base is the formate ion (HCOO⁻).
2. **Acetic Acid (CH₃COOH)**: The conjugate base is the acetate ion (CH₃COO⁻).
3. **Benzoic Acid (C₆H₅COOH)**: The conjugate base is the benzoate ion (C₆H₅COO⁻).

### Step 2: Analyze the Conjugate Bases
- **Formate Ion (HCOO⁻)**: This ion has minimal electron-donating effects, leading to a relatively stable structure.
- **Acetate Ion (CH₃COO⁻)**: The presence of the methyl group (CH₃) has a +I (inductive) effect, which increases the electron density on the oxygen and makes it less stable compared to the formate ion.
- **Benzoate Ion (C₆H₅COO⁻)**: This ion is stabilized by resonance due to the aromatic ring. The resonance allows for delocalization of negative charge, making it more stable than both formate and acetate ions.

### Step 3: Compare the Acidity
- **Benzoic Acid vs. Acetic Acid**: Benzoic acid is more acidic than acetic acid because the benzoate ion is resonance-stabilized, while the acetate ion is destabilized by the +I effect of the methyl group.
- **Formic Acid vs. Benzoic Acid**: Formic acid is more acidic than benzoic acid because it lacks the electron-donating effects present in benzoic acid. The formate ion is more stable than the benzoate ion due to the absence of resonance destabilization.

### Step 4: Establish the Order of Acidity
Based on the analysis:
- Formic Acid (HCOOH) > Benzoic Acid (C₆H₅COOH) > Acetic Acid (CH₃COOH)

### Conclusion
The correct order of acidity is:
**Formic Acid > Benzoic Acid > Acetic Acid**