Adipic acid dinitrile

Fig. 7.6. Industrial-scale processing condensation of adipic acid (B) and ammonia to adipic acid diamide (D) and its thermal dehydration to adipic acid dinitrile (C). On a very large scale, adipic acid dinitrile is hydrated to give 1,6-diamino-hexane ("hexamethylenedi-amine ), which is further processed to furnish nylon-6,6 ("nylon").

Actually, the technical synthesis of adipic acid dinitrile does not begin with, but proceeds via adipic acid diamide (D). In fact, it starts with the bis(ammoniumcarboxylate) A obtained from adipic acid (B) and two equivalents of ammonia. Upon heating in a closed reactor small amounts of the carboxylic acid and ammonia are regenerated from the salt A and react according to the Bac2 mechanism (Figure 6.24) to give diamide D. 

The synthesis of adipic acid dinitrile outlined in Figure 7.7 proceeds under milder conditions than the one presented in Figure 7.6. Here, the starting material includes adipic acid (B) and urea (C). Since urea can only be protonated by mineral acids, the formation of the ammo-nium salt A is impossible. This means that the entire reactor space is available for the initial... 

Fig. 7.7. Laboratory method for the synthesis of adipic acid dinitrile (D). Condensation of adipic acid (B) and urea to give adipic acid diamide (E) and its thermal dehydration. The reaction F — H—as well as its mechanism—corresponds to the reversal of the formation of biuret that takes place upon the heating of urea (mechanistic details conversion of M —> 0 in Figure 8.3).

SYNS ADIPIC ACID DINITRILE ADIPIC ACID NITRILE ADIPODINITRILE 1,4-DICYANOBUTANE HEXANEDINTTRILE HEXANEDIOIC ACID DINITRILE NITRILE ADIPICO (ITALIAN) TETRAMETHYLENE CYANIDE... 

Synonyms Adipic acid dinitrile Adipic acid nitrile 1,4-Dicyanobutane Hexanedinitrile Tetra-methylene cyanide Chemical Formula C6HgN2... 

Hydrogenation benzene, adipic acid dinitrile, nitroaromatics, glucose, ammonium nitrate, unsaturated fatty acids cyclohexane, hexamethylene diamine, amines, sorbitol, hydroxyl amines... 

ADIPIC ACID DINITRILE or ADIPIC ACID NITRILE... 

Beilstein Handbook Reference) Adipic acid dinitrile Adipinsaeuredinitril Adipodinitrile Adiponitrile Adipyidinitrile AI3-11080 BRN 1740005 CCRIS 4570 1,4-Dicyanobutane EINECS... 

Synonyms 1,4-dicyanobutane hexanedini-trile adipic acid dinitrile tetramethylene cyanide... 

Adipic acid dinitrile. See Adiponitrile Adipic acid, dipropyl ester. See Dipropyl adipate... 

Hydrogenation of adipic acid dinitrile to hexamethylene diamine... 

Reactions of this type are called electrochemical hydrodimerization. They are of great value for the synthesis of various bifunctional compounds. A reaction that has found wide commercial nse is the hydrodimerization of acrylonitrile to adiponitrile (the dinitrile of adipic acid) ... 

Hexamethylenediamine (HMDA), a monomer for the synthesis of polyamide-6,6, is produced by catalytic hydrogenation of adiponitrile. Three processes, each based on a different reactant, produce the latter coimnercially. The original Du Pont process, still used in a few plants, starts with adipic acid made from cyclohexane adipic acid then reacts with ammonia to yield the dinitrile. This process has been replaced in many plants by the catalytic hydrocyanation of butadiene. A third route to adiponitrile is the electrolytic dimerization of acrylonitrile, the latter produced by the ammoxidation of propene. 

Many hydrogenation and polymerization reactions in the chemical industry are carried out with liquid-phase reactants. An example is the hydrogenation of aliphatic dinitriles to produce diamines (108,109), which are subsequently converted with adipic acid in solution and polymerized to produce linear polyamides, including nylon 6,6. Recently, the development of wet-environmental transmission electron microscopy (wet-ETEM) for direct nanoscale probing of... 

The diamines needed for the polyamides can be made by conversion of the acids to their ammonium salts followed by heating to form the dinitriles, which can then be reduced. Adipic acid can be reduced to 1,6-hexanediol (for use in polyurethanes) with hydrogen in 95% yield using a modified platinum catalyst.38 Earlier processes, which... 

In the earlier vapor phase process, a mixture consisting of ammonia and adipic acid in a volumetric ratio of 20/1 was sent between 300 and 350 C to a catalyst bed based on phosphoric acid and boron. The thermal decomposition which occurred upon the vaporization of adipic acid limited the dinitrile molar selectivity to 80 per cent. The new liquid phase process, developed by IC1 (Imperial Chemical Industries) and Monsanto, operates in the molten acid between 200 and 300°C. in the presence of phosphoric acid. The selectivity to adiponitrile, purified by distillation and recrystallization, is 90 molar per cent. 

Common monomers for copoly(amide)s are adipic acid, TPA, hexa-methylenediamine (HMD) and e-caprolactam." 2-Methylpentamethylene-diamine and 2-ethyltetramethylenediamine are used for transparent PPA in combination with IPA. These diamines can be prepared by hydrogenation of the corresponding dinitriles. For example, 2-methylpentamethyl-enediamine can be prepared by hydrogenating 2-methyleneglutaric dinitrile, which is a dimerization product of acrylonitrile. 

Although nylon intermediates are aliphatic, the main starting materials are aromatic hydrocarbons. In the earliest processes, phenol was hydrogenated (over nickel or palladium) to cyclohexanone/ol mixtures, known as KA oil , which gave adipic (hexanedioic) acid on oxidation with nitric acid. Half of this adipic acid was converted to the dinitrile, by vapour phase reaction with ammonia. Finally the dinitrile was hydrogenated to hexamethylenediamine (1,6-diaminohexane). Nylon-6,6 is produced by the condensation of essentially equimolar quantities of adipic acid and the diamine. 

This process is by no means as simple as this equation implies, with the formation of several isomers, and hence the need for interconversions at each stage. Both processes take the pressure off benzene, from which the multistage processes gave poor yields of dinitrile (c. 50% of theory). In a somewhat similar manner, BASF have operated a semi-commercial plant to produce adipic acid by the bis-hydrocarboxylation of 1,3-butadiene ... 

The Du Pont process for the manufacture of adiponitrile (1,4-dicyanobutane) from butadiene depends on nickel catalysed hydrocyanation. Adiponitrile is the precursor to 1,6-diaminohexane which is used to make Nylon 6,6. The other component, adipic acid (1,6-hexanedioic acid) is usually made by oxidation of cyclohexane, although in principle it could also be obtained from the dinitrile. The... 

The resulting dinitrile can be hydrolyzed to adipic acid, HOOC(CH2)4 COOH, or reduced to hexamethylenediamine, H2N(CH2)6NH2, the two components needed for the production of nylon. 

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