Salicylic acid/Aspirin
Salicylic acid is an organic acid that has a colorless crystalline structure and is poorly soluble in water. Salicylic acid is a beta-hydroxy acid, which is a larger molecule than alpha-hydroxy acids and is widely used in topical formulations as a comedolytic and keratolytic agent. Beta-hydroxy acids are derived from plant hormones and are lipid soluble. Salicylic acid, or 2-hydroxybenzoic acid, is extracted from the bark of the willow tree, and systemic formulations provide pain relief and anti-inflammatory effects. Salicylic acid applied topically penetrates pores which contain sebum, thereby softening and removing the epithelium. Its larger molecular size limits penetration through the dermis to general circulation. Salicylic acid has been combined effectively with other ingredients for various topical applications. Salicylic acid is reacted with acetic anhydride to produce acetyl salicylic acid .Salicylic acid is used in the pharmaceutical sector as an antiseptic, disinfectant and anti-fungal agent. It is applied externally as a dusting powder, lotion or ointment for the treatment of dandruff, eczema, psoriasis and parasitic skin diseases. To destroy warts or crone, it is applied in a collusion or as a plaster. Salicylic acid has been shown to be effective in dermatologic and cosmetic applications for its rapid effect as a keratolytic agent. Products containing salicylic acid include facial cleansers and antidandruff shampoos. Salicylic acid has been added in trace amounts as a food preservative and in mild antiseptics, such as mouthwashes and toothpastes. Salicylic compounds have also been synthesized for analgesics and antipyretics . Aspirin is the most widely used over-the-counter drug in the world. The average tablet contains about 325 milligrams of acetylsalicylic acid with an inert binding material such as starch. Aspirin is used to relieve pain, reduce inflammation, and lower fever. Aspirin originally was derived by boiling the bark of the white willow tree. Although the salicylic in willow bark has analgesic properties, purified salicylic acid was bitter and irritating when taken orally. Salicylic acid was neutralized with sodium to produce sodium salicylate, which was better-tasting but still irritated the stomach. Salicylic acid could be modified to produce phenylsalicylate, which was better tasting and less irritating, but released the toxic substance phenol when metabolized. Demand trend of most salicylic acid is used as raw material for producing aspirin and a small amount of salicylic acid is sold as chemical raw material. So, the demand of salicylic acid is closely related to the output of aspirin. Manufacturing process of salicylic acid include three reaction steps involved in producing salicylic acid from the starting material namely phenol. First, sodium phenolate is prepared by reacting phenol and aqueous sodium hydroxide. The resulting solution is heated and evaporated to dryness. Second, a direct solid gas reaction between sodium phenolate and carbon dioxide is performed, producing sodium salicylate. Third, the sodium salicylate is dissolved in water and converted to salicylic acid by acidification with sulphuric Acid. Manufacturing process of aspirin is when salicylic acid is treated with acetic anhydride, causing a chemical reaction that turns salicylic acid's hydroxyl group into an ester group R-OH -> R-OCOCH3.