What is the Difference Between Salicylic Acid and Benzoic Acid?

Salicylic acid and benzoic acid are both organic compounds with similar chemical structures. However, there are some key differences between them:

1. Chemical Structure: Salicylic acid has a –OH group, while benzoic acid has no –OH groups in its ring structure. Salicylic acid is also known as ortho-hydroxybenzoic acid or 2-hydroxybenzoic acid.
2. Acidity: Salicylic acid is stronger than benzoic acid due to the presence of a stable conjugate base. This makes salicylic acid more acidic than benzoic acid.
3. Usage: Salicylic acid is primarily used as a medication to remove the outer layer of skin, treating warts, acne, ringworm, and producing aspirin. It is also used as a food preservative. Benzoic acid, on the other hand, is important in the production of phenol, plasticizers, and sodium benzoate, which is a useful food preservative.

In summary, salicylic acid and benzoic acid have similar chemical structures but differ in the presence of a hydroxyl group, acidity, and their respective uses.

Comparative Table: Salicylic Acid vs Benzoic Acid

The key difference between salicylic acid and benzoic acid is the presence of a hydroxyl group in salicylic acid, whereas benzoic acid has no hydroxyl groups in its structure. Here is a comparison table highlighting the differences between salicylic acid and benzoic acid:

Both salicylic acid and benzoic acid are carboxylic acids with a benzene ring as the base structure. They have closely similar chemical structures but differ in the presence of a hydroxyl group and their acidity. Salicylic acid is more acidic than benzoic acid, with a pKa value of 2.97 compared to benzoic acid's pKa value of 4.20.