What is Salicylic Acid?

Salicylic acid is naturally synthesized by certain plants (like Willow's bark), we find it in the form of esterified methyl salicylate. It can act as a hormonal signal that trigger thermogenesis.

In large quantities, it is a toxic product, but in lower quantities it is used as a food preservative and antiseptic.

The medical properties of salicylic acid are known for a long time, especially for its action against fever. It is extracted mainly from willow, salix in latin which it takes its name. In its fight against fever, it is now supplanted by other more effective drugs like aspirin (which is a derivative of salicylic acid), or paracetamol.

It is no longer used for its soothing effect (analgesic) and it is found in many dermatology products, in addition to another active ingredient. For example, it is used in the treatment of acne, warts or hyperhydrosis.

This group of carboxylic acid (-COOH) may react with alcohol to produce esters. The hydroxy group may react with acetic acid to form acetylsalicylic acid, or aspirin.

Salicylic acid is used for the production of coloring agents, fragrances and acetylsalicylic acid (ASA, better known under the brand name Aspirin ®) to relieve pain and as anti-inflammatory drug. In the form of insoluble salt, the bismutsubsalicylat it is used against diarrhea and disorders of the gastrointestinal. It is also used for the treatment of hyperkeratosis, for example, in the treatment of acne and warts. Salicylic acid may prevent bacterial growth and its usage as a preservative in food is already prohibited.

Salicylic acid is a form organic acid, it can synthesized biologically from the an amino acid called phenylalanine.

To produce Salicylic acid, Sodium salicylate is created by exposing sodium phenoxide with CO² at high temperature and high pressure by using the Kolbe-Schmitt reaction. The product will be acidified to produce synthetic salicylic acid:

It can also be reversely produced by conducting a hydrolysis of Aspirin (acetylsalicylic acid) or methyl salicylate (Oil of Wintergreen) with any strong acid or base.

Salicylic acid reacts with an alcohol to form a salicylic acid ester. Salicylic esters are mainly used in the cosmetics and perfume industry or as additives in bathing ointments or creams, as well as fragrance and UV filters in sunscreen products. The most famous ester of salicylic acid is aspirin. It was here that the hydroxyl group of salicylic acid reacts with the Carboxyl ester to form acetic acid.