Adiponitrile, preparation

The hexamethylenediamine used with adipic acid to make nylon-6,6 is made by reduction of adiponitrile, prepared, in turn, by the addition of hydrogen cyanide to 1,3-... 

Enone formation-aromatization has been used for the synthesis of 7-hydro-xyalkavinone (716)[456]. The isotlavone 717 was prepared by the elimina-tion[457]. The unsaturated 5-keto allyl esters 718 and 719, obtained in two steps from myreene. were subjected to enone formation. The reaction can be carried out even at room temperature using dinitriles such as adiponitrile (720) or 1,6-dicyanohexane as a solvent and a weak ligand to give the pseudo-ionone isomers 721 and 722 without giving an allylated product(458]. 

Uses. The principal use of adiponitrile is for hydrogenation to hexamethylene diamine leading to nylon-6,6. However, as a result of BASE s new adiponitrile-to-caprolactam process, a significant fraction of ADN produced may find its way into nylon-6 production. Adipoquanamine, which is prepared by the reaction of adiponitrile with dicyandiamide [461-58-5] (cyanoguanidine), may have uses in melamine—urea amino resins (qv) (see "Benzonitrile, Uses"). Its typical Hquid nitrile properties suggest its use as an extractant for aromatic hydrocarbons. 

Hexamethylenediamine may be conveniently prepared from adipic acid via adiponitrile... 

In a typical process adiponitrile is formed by the interaction of adipic acid and gaseous ammonia in the presence of a boron phosphate catalyst at 305-350°C. The adiponitrile is purified and then subjected to continuous hydrogenation at 130°C and 4000 Ibf/in (28 MPa) pressure in the presence of excess ammonia and a cobalt catalyst. By-products such as hexamethyleneimine are formed but the quantity produced is minimized by the use of excess ammonia. Pure hexamethylenediamine (boiling point 90-92°C at 14mmHg pressure, melting point 39°C) is obtained by distillation, Hexamethylenediamine is also prepared commercially from butadience. The butadiene feedstock is of relatively low cost but it does use substantial quantities of hydrogen cyanide. The process developed by Du Pont may be given schematically as ... 

Adiponitrile, a starting material used in the manufacture of nylon, can be prepared in three steps from 1,3-butadiene. How would you carry out this synthesis ... 

A process for the hydrogenation of adiponitrile and 6-aminocapronitrile to hexamethylenediamine in streams of depolymerized Nylon-6,6 or a blend of Nylon-6 and Nylon-6,6 has been described. Semi-batch and continuous hydrogenation reactions of depolymerized (ammonolysis) products were performed to study the efficacy of Raney Ni 2400 and Raney Co 2724 catalysts. The study showed signs of deactivation of Raney Ni 2400 even in the presence of caustic, whereas little or no deactivation of Raney Co 2724 was observed for the hydrogenation of the ammonolysis product. The hydrogenation products from the continuous run using Raney Co 2724 were subsequently distilled and the recycled hexamethylenediamine (HMD) monomer was polymerized with adipic acid. The properties of the polymer prepared from recycled HMD were found to be identical to that obtained from virgin HMD. 

Polymers derived from the preceding type of reaction with nitriles,5 amines,6 and phosphines,7 have been reported. Green8 has reported the preparation of a resin-type material composed of at least 10 repeat units from the reaction between decaborane and adiponitrile (NC(CH2)4CN). Also reported,9 is the inclusion of flexible siloxanes and ether linkages into a diamine, and of their subsequent reaction with decaborane to give adduct polymers (see 2, 3). 

Electrohydrodimerization is well known for its application in the preparation of adiponitrile [82]. The method was successfully used in the preparation of heterocycles from reductions of activated bis-alkenes (Scheme 60 and vide supra Scheme 6) [10, 83] or bis-imines affording substituted piperazines in good yields, in the presence of proton donors (Scheme 61) [84]. 

Without doubt, this is the best known cathodically-initiated cyclization. The transformation corresponds to the intramolecular variation of electrohydrodimerization [11-13], a process well known for its application to the preparation of adiponitrile [14]. 

A synthesis of great industrial interest is the electrochemical anodic reductive dimerisation of two molecules of acrylonitrile to give adiponitrile, from which adipic acid and 1,6-hexanediamine are prepared by hydrolysis and reduction, respectively, of the two nitrile groups. Polycondensation of the resulting products leads to Nylon 66 (Scheme 5.27). 

Hydrogen cyanide in pure form was prepared first in 1815 by Gay-Lussac. Earher, in 1782, Scheel prepared this compound in dilute solution. The most important apphcation of hydrogen cyanide is to produce methyl methacrylate for methacrylate resins and plastics. Other products made from hydrogen cyanide include potassium cyanide, sodium cyanide, adiponitrile, methionine, cyanuric chloride, cyanogen, nitrilotriacetic acid, and several triazine pesticides. The compound also is used in small amounts for extermination of rodents. 

Acrylonitrile is a monomer used in high volume principally in the manufacture of acrylic fibres, resins (acrylonitrile-butadiene-styrene, styrene-acrylonitrile and others) and nitrile rubbers (butadiene-acrylonitrile). Other important uses are as an intermediate in the preparation of adiponitrile (for nylon 6/6) and acrylamide and, in the past, as a fumigant. Occupational exposures to acrylonitrile occur in its production and use in the preparation of fibres, resins and other products. It is present in cigarette smoke and has been detected rarely and at low levels in ambient air and water. 

Uses. The principal use of adiponitrile is for hydrogenation to hexamethylene diamine leading to nylon-6,6. Adipoquanamine, prepared by the reaction of adiponitrile with dicyandiamide (cyanoguanidine), has typical liquid nitrile properties that suggest its use as an extractant for aromatic hydrocarbons. 

Ruthenium-catalyzed hydrodimerization of acrylonitrile under hydrogen atmosphere to give adiponitrile (393) is a useful coupling reaction [154], Dimethyl hexenedioates (394a and 394b) are formed by dimerization of methyl acrylate by Pd, Ru and Rh catalysts. In particular the catalyst prepared by the treatment of RuC12 with Zn and... 

Catalytic hydrogenation of nitriles has long been used for the preparation of various amines. It is performed over metallic catalysts mostly in the liquid phase. The method is also of industrial importance and has been applied to the commercial production of various amines, for example, various aliphatic amines from fatty acid nitriles, hexa-methylenediamine (1,6-hexanediamine) from adiponitrile, and xylene-a,a -diamines [bis(aminomethyl)benzenes] from the corresponding phthalonitriles. 

Aminocyclopentenecarbonitrile, which is prepared by Thorpe cyclization of adiponitrile, reacts with acid anhydrides to give 2-(acylamino)cyclopentenecarbonitriles (87).74 Excellent yields of 4-amino-2-hydroxy-6,7-dihydro-5/y-l-pyrindines (88-91) are obtained when derivatives of 87 are treated with sodamide in liquid ammonia... 

Owing to its high reactivity, numerous applications and interesting syntheses have been discovered, for example, much effort has been devoted to the preparation of adiponitrile (a nylon-6, 6>precursor) by (he catalytic addition of HCN to butadiene (a particularly cheap petrochemical diolefin). 

This type of reaction is now of major industrial importance because it constitutes a straiglitforward synthesis of nitriles. Wlien it is applied to a diolefm, such as butadiene, it leads to the formation of dinitriles, which are precursors of valuable monomers for the preparation of polymers (butadiene leads to adipo-nilrile. a nylon-b, fvprecursor). Du Font developed the first commercial process using butadiene and HCN for adiponitrile synthesis from butadiene, but this process does nut proceed through a hydrocyanation reaction it is. in fact, a copper-catalyzed halogenation reaction followed by a cyanaikm reaction (tquaiion (16)) of the chlorinated intermediate (Fquation (17)). 

Obviously, the direct addition of two molecules of HCN to butadiene (a true hydrocyanation process) is a more straightforward method for the preparation of adiponitrile than the former process, which requires three steps. 

A new route to prepare nicotinic acid starts from 2-methylglutaronitrile, a major side-product in the adiponitrile process and, as such, a readily available starting-material. It is easily hydrogenated to 2-methylpentanediamine, which is then condensed to methyl piperidine and dehydrogenated to 3-picoline. The gas-phase ammoxidation of the latter to cyanopyridine is followed by hydrolysis to either nicotinamide or nicotinic acid (Scheme 20.4). The cyanopyridine route for the production of nicotinic acid has the advantage of a significantly better selectivity with respect to the direct oxidation route from 3-picoline owing to the easy decar-... 

Irreversible electrode reactions predominate in preparatively oriented organic electrochemistry [4,67]. Examples are the cathodic hydrodimerization of acrylonitrile to yield adiponitrile ... 

Other products of an alkali amalgam decomposition process are sodium sulfide from polysulfide solutions, sodium dithionide from hydrogen sulfide, hydra-zobenzene or aniline from nitrobenzene, and adiponitrile from acrylonitrile. Last but not least alkali metals can be prepared directly from the amalgam [33]. 

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