Dicarboxylic acid

Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group. Dicarboxylic acids can be used to prepare copolymers such as polyamides and polyesters.

In general, dicarboxylic acids show the same chemical behaviour and reactivity as monocarboxylic acids. The ionization of the second carboxyl group occurs less readily than the first one. This is because more energy is required to separate a positive hydrogen ion from the anion than from the neutral molecule.

A mnemonic to aid in remembering the order of the common nomenclature for the first six dicarboxylic acids is "Oh my, such great apple pie!" (oxalic, malonic, succinic, glutaric, adipic, pimelic). A variant adds "Sweet as sugar!" (suberic, azelaic, sebacic) to the end of the mnemonic. An additional way of remembering the first six dicarboxylic acids is by simply recalling the acronym OMSGAP, which is a simplification of the previously described mnemonic device.

When one of the carboxy groups is replaced with an aldehyde group, the resulting structure is called a "aldehydic acid".

Simple forms of dicarboxylic acids

Short-chain dicarboxylic acids are of great importance in the general metabolism and up to n=3 they cannot be considered as lipids since their water solubility is important. The simplest of these intermediates is oxalic acid (n=0), the others are malonic (n=1), succinic (n=2) and glutaric (n=3) acids.

The other lipid members of the group found in natural products or from synthesis have a "n" value from 4 up to 21.
Adipic acid (n=4) : Despite its name (in Latin adipis is fat), this acid (hexanedioic acid) is not a normal constituent of natural lipids but is a product of oxidative rancidity (lipid peroxidation). It was obtained [1] by oxidation of castor oil with nitric acid (splitting of the carbon chain close to the OH group). Synthesized in 1902 from tetramethylene bromide, it is now obtained by oxidation of cyclohexanol or cyclohexane. It has several industrial uses in the production of adhesives, plasticizers, gelatinizing agents, hydraulic fluids, lubricants, emollients, as an additive in the manufacture of some form of nylon (nylon-6,6), polyurethane foams, leather tanning, urethane and also as an acidulant in foods. Adipic acid is used after esterification with various groups such as dicapryl, di(ethylhexyl), diisobutyl, and diisodecyl.
Pimelic acid (n=5) : this acid (heptanedioic acid), from the Greek pimelh (pimele fat), as adipic acid, was isolated from oxidized fats. It was obtained in 1884 by Ganttner F et al.[2] as a product of ricinoleic acid (hydroxylated oleic acid) from castor oil.
Suberic acid (n=6) : it was firstly produced by nitric acid oxidation of cork (Latin suber) material and then from castor oil [3]. The oxidation of ricinoleic acid produces, by splitting at the level of the double bond and at the level of the OH group, at the same time, suberic acid (octanedioic acid) and the next homologue azelaic acid. Suberic acid was used in the manufacture of alkyd resins and in the synthesis of polyamides leading to nylon.
Azelaic acid (n=7) : nonanedioic acid is the best known dicarboxylic acid. Its name stems from the action of nitric acid (azote, nitrogen, or azotic, nitric) oxidation of oleic or elaidic acid. It was detected among products of rancid fats [4]. Its origin explains for its presence in poorly preserved samples of linseed oil and in specimens of ointment removed from Egyptian tombs 5000 years old [5]. Azelaic acid was prepared by oxidation of oleic acid with potassium permanganate [6], but now by oxidative cleavage of oleic acid with chromic acid or by ozonolysis. Azelaic acid is used, as simple esters or branched-chain esters) in the manufacture of plasticizers (for vinyl chloride resins, rubber), lubricants and greases. Azelaic acid is now used in cosmetics (treatment of acne). It displays bacteriostatic and bactericidal properties against a variety of aerobic and anaerobic micro-organisms present on acne-bearing skin. . Azelaic acid was identified as a molecule that accumulated at elevated levels in some parts of plants and was shown to be able to enhance the resistance of plants to infections [7].
Sebacic acid (n=8) : decanedioic acid was named by Thenard LJ (1802) from the Latin sebaceus(tallow candle) or sebum (tallow) in reference to its use in the manufacture of candles. Thenard LJ isolated this compound from distillation products of beef tallow. In 1954, it was reported that it was produced in excess of 10,000 tons annually by alkali fission of castor oil [8]. Sebacic acid and its derivatives, as azelaic acid, have a variety of industrial uses as plasticizers, lubricants, diffusion pump oils, cosmetics, candles, etc. It is also used in the synthesis of polyamide, as nylon, and of alkyd resins. An isomer, isosebacic acid, has several applications in the manufacture of vinyl resin plasticizers, extrusion plastics, adhesives, ester lubricants, polyesters, polyurethane resins and synthetic rubber.
Dodecanedioic acid (n=10) : that acid is used in the production of nylon (nylon-6,12), polyamides, coatings, adhesives, greases, polyesters, dyestuffs, detergents, flame retardants, and fragrances. It is now produced by fermentation of long-chain alkanes with a specific strain of Candida tropicalis [9]. Its monounsaturated analogue (traumatic acid) is described below.