Adipic acid is a white crystalline organic compound with the formula C6H10O4. Adipic acid, a strong acid, is used in many areas in industry and daily life. Adipic acid is a chemical that rarely occurs in nature. It has a sour taste. It is typically found exogenously in both urine and blood. Adipic acid was discovered in France in 1834 as a result of the oxidation of an oil. The chemical and physical properties of adipic acid are:

• Its molecular weight is 146.14 g/mol.
• Its melting point is 152 °C.
• Its boiling point is 337.5 °C.
• Its density is 1.36 g/mL.
• Its solubility is moderate in water and alcohol, and low in ether.
• pKa values are 4.41 and 5.41.

The production methods of adipic acid are as follows:

• Cyclohexane method: This is the most common production method of adipic acid. Adipic acid is obtained by oxidation of cyclohexane with air or nitric acid. This method also produces nitrous gas.
• Phenol method: This is an alternative production method of adipic acid. Adipic acid is produced by oxidation of phenol with oxygen using catalysts. This method also produces water.
• Biochemical synthesis: This is an innovative production method of adipic acid. Adipic acid is produced by fermentation of glucose from biomass such as sugar or starch by microorganisms. This method also produces carbon dioxide and water.

Among the uses of adipic acid are the following:

• Nylon industry Adipic acid is one of the most widely used raw materials in the nylon industry. It reacts with hexamethylene diamine to form the polymer nylon 6,6. Nylon 6,6 is used in products such as fibers, clothing, plastics, filaments, food packaging and rope.
• Polyurethane industry: Adipic acid also plays an important role in the polyurethane industry. It is used in the synthesis of polyester polyols. Polyester polyols are used in products such as foam, shoe soles, adhesives and sealants.
• Food industry: Adipic acid is one of the most widely used additives in the food industry. Adipic acid is used to give foods a sour taste, to regulate acidity, as a buffering agent, and as a gelling agent. For example, adipic acid is used in products such as jams, preserves, confectionery, frozen foods, fruit juices and instant teas.
• Cleaning industry Adipic acid is also used as an effective agent in the cleaning industry. Adipic acid is used to remove rust from metal surfaces, remove lime stains and prevent bad odors.
• Corrosion inhibitor industry: Adipic acid is also used in the corrosion inhibitor industry. It is used as an intermediate in corrosion inhibitors to protect metals against corrosion and dulling by acid vapors in water treatment systems, steam boiler water treatment systems and aqueous hydraulic fluids.