Although p-hydroxy benzoic acid is less acidic than benzoic acid, ortho hydroxy benzoic acid (salicylic acid) is about 15 times more acidic than benzoic acid. Explain.

Explanation

To understand why p-hydroxybenzoic acid is less acidic than benzoic acid while ortho-hydroxybenzoic acid (salicylic acid) is significantly more acidic than benzoic acid, we need to analyze the structural and electronic effects of the hydroxyl (-OH) group in both cases.

### Step 1: Understanding Acidity
Acidity in organic compounds is primarily determined by the stability of the conjugate base formed after the acid donates a proton (H+). The more stable the conjugate base, the stronger the acid.

### Step 2: Analyzing p-Hydroxybenzoic Acid
p-Hydroxybenzoic acid has the -OH group positioned para to the carboxylic acid (-COOH) group. When p-hydroxybenzoic acid loses a proton, it forms the p-hydroxybenzoate ion. The -OH group in the para position does not significantly stabilize the negative charge on the carboxylate ion because it cannot effectively participate in resonance with the -COO- group.

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