Adipic acid

Adipic acid (IUPAC systematic name: hexanedioic acid) is a chemical compound of the class of carboxylic acids. It is a white crystalline powder appearing as an acid in aqueous circumstances, though it is not highly soluble.

Preparation
Historically, adipic acid is prepared from various fats using oxidation. Current commercial adipic acid is produced from cyclohexane by two oxidation steps.


 * 1) Cyclohexane + O2 → cyclohexanol and cyclohexanone
 * 2) cyclohexanol/cyclohexanone + nitric acid + air → adipic acid + nitrous oxide

(The mixture of cyclohexanol and cyclohexanone produced from cyclohexane is commercially called "KA oil", the abbreviation of "Ketone-Alcohol oil".)

Utilizing Principles of Green chemistry, a new method of synthesis involves:

Cyclohexene + hydrogen peroxide with a tungsten catalyst under phase transfer conditions to produce adipic acid. The waste product is water.

Uses
By far the main use of adipic acid is as monomer for the production of nylon by a polycondensation reaction with hexamethylene diamine forming 6,6-nylon, the most common form of nylon. Other uses include:


 * Monomer for production of Polyurethane


 * reactant to form plasticizers and lubricant components


 * Food Ingredient as a flavorant and gelling aid.E-number E355.


 * FDA citations - GRAS (21 CFR 184.1009), Indirect additive (21 CFR 175.300, 21 CFR 175.320, 21 CFR 176.170, 21 CFR 176.180, 21 CFR 177.1200, 21 CFR 177.1390, 21 CFR 177.1500, 21 CFR 177.1630 , 21 CFR 177.1680, 21 CFR 177.2420, 21 CFR 177.2600)