Adipic acid

Colorless and odorless solid

Fixed

1.37 g · cm -3

151 ° C

331 ° C

10,3 Pa ( 20 ° C)

  • PKS1 = 4.43
  • PKa2 = 5.42
  • Poorly in cold water ( 24 g · l-1 at 20 ° C)
  • 160 g · l-1 in warm water ( 60 ° C)

Attention

1900 mg · kg -1 ( LD50, mouse, oral)

Template: Infobox chemical / molecular formula search available

Adipic acid, also hexanedioic, is a dicarboxylic acid. Their esters and salts are referred to as Adipates.

Properties

Adipic acid, HOOC- (CH2) 4 -COOH, forms colorless crystals ( monoclinic), which melt at 152 ° C and have a long-lasting, sour taste.

Production and reserves

Adipic acid is obtained by oxidation of cyclohexene or cyclohexanol with nitric acid or potassium permanganate, in nature it comes in appreciable amounts in sugar beet and beetroot before. Alternatively, offers a production of furfural, furfural is decarbonylated in over a ZnO - Cr2O3 contact. With the furan obtained can now with HCl ether cleavage ( favored by the diene character ) can be performed. After a reaction with sodium cyanide and complete hydrolysis also obtained adipic acid. Moreover, large quantities of adipic acid are produced by hydrolysis of adiponitrile.

Use

Adipic acid is particularly an intermediate for nylon. This plastic material is formed as a condensation product of adipic acid and hexamethylene diamine with elimination of water. The monomeric intermediate hexamethylenediamine adipate is also called AH- salt, and results from the first letter of the components. Adipic acid is used as intermediate for the production of polyester polyols for polyurethane systems and thermoplastic polyurethanes. Main applications are elastomers, flexible and rigid foams. High-boiling esters of adipic acid, in particular diethylhexyl adipate, may be used as a substitute for phthalic acid esters as plasticizers for polyvinylchloride (PVC).

Adipic acid is approved in the EU as a food additive (E 355 ) and is used as such as an acidulant, as well as their alkali metal salts sodium adipate (E 356) and potassium adipate (E 357) and is sometimes used as a substitute for tartaric acid in the baking powder and soda.

In addition, adipic acid is used as an additive in the flue gas desulfurization, in order to raise the separation efficiency of over 99% limestone scrubbers. The task of adipic acid is mainly to provide a pH buffer.

By heating the salt of adipic acid cyclopentanone may be prepared synthetically.

CAS registry number PubChem Vapor pressure Dangerous Substances Directive (67/548/EEC) Decarbonylation Digital Object Identifier Integrated Authority File
29862
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