Chemistry:2-Methyleneglutaronitrile

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2-Methyleneglutaronitrile
2-Methylenglutaronitril Struktur.svg
Names
Preferred IUPAC name
2-Methylidenepentanedinitrile
Other names
2,4-dicyano-1-butene
2-Methylenepentanedinitrile
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
EC Number
  • 216-391-8
UNII
Properties
C6H6N2
Molar mass 106.13 g·mol−1
Appearance clear, colourless[1] liquid
Density 0.976 g·cm−3 (25 °C)[2]
Hazards
GHS pictograms GHS07: Harmful
GHS Signal word Warning
H302, H312, H332
P261, P264, P270, P271, P280, P301+312, P302+352, P304+312, P304+340, P312, P322, P330, P363, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Tracking categories (test):

2-Methylene glutaronitrile is a dimerization product of acrylonitrile and a starting material for di- and triamines, for the biocide 2-bromo-2-(bromomethyl)pentanedinitrile and for heterocycles, such as 3-cyanopyridine.

Preparation

2-Methylene glutaronitrile is a side-product in the production of hexanedinitrile which is used (after hydrogenation to 1,6-diaminohexane) as a key component for engineering polymers such as the polyamides (PA 66) or polyurethanes. Hexanedinitrile can be industrially produced by electrochemical hydrodimerisation or by catalytic dimerization of acrylonitrile.

A catalytic tail-tail dimerization of two acrylonitrile molecules forms hexanedinitrile:

Hydrodimerisierung von Acrylnitril zu Adiponitril

Also head-to-tail dimerization can occur in the process. In the presence of tricyclohexylphosphine (PCy3) a yield of up to 77% 2-methylene glutaronitrile can be obtained:[3]

Dimerisierung von Acrylnitril zu 2-Methylenglutaronitril

Metal halides (such as zinc chloride[4][5] or aluminium chloride[6]) are used with tertiary amines (such as triethylamine) as catalysts for the dimerization. Crude yields of up to 84% are achieved.[4] Often, significant amounts of product are lost during the work-up (e. g. extraction and distillation) because of the tendency to polymerization of 2-methylene glutaronitrile.

In addition to the linear dimerization products 1,4-dicyano-2-butene and 1,4-dicyano-3-butene (obtained as cis-trans isomer mixtures) usually also other oligomers (and polymers) of acrylonitrile are formed. During the electrochemical hydrooligomerization of acrylonitrile, these are trimers, such as 1,3,6- and 1,3,5-tricyanohexane or tetramers, such as 1,3,6,8- and 1,3,5,8-tetracyanooctane.[7] The reaction of acrylonitrile with tributylphosphine affords 2-methyleneglutaronitrile in a modest yield of about 10% after fractional distillation.[8] The DABCO-catalyzed acrylonitrile dimerization of 2,4-dicyano-1-butene after 10 days at room temperature is with 40% yield similarly inefficient.[9]

Use

The earlier patent literature describes processes for the isomerization of 2-methylene glutaronitrile to 1,4-dicyanobutenes as hexanedinitrile precursors, which became obsolete with the optimization of the electrochemical hydrodimerization of acrylonitrile to hexanedinitrile.[10]

The electrochemical hydrodimerization of 2-methylene glutaronitrile produces 1,3,6,8-tetracyanooctane.[8]

Hydrodimerisierung von 2-Methylenglutaronitril

In the hydrogenation of 2-methylene glutaronitrile in the presence of palladium on carbon, hydrogen is attached to the double bond and 2-methylglutaronitrile is obtained in virtually quantitative yield.[11]

The hydrogenation of the nitrile groups requires more severe conditions and the presence of ammonia or amines to suppress the formation of secondary amines. This second hydrogenation step is carried out with Raney-cobalt as the hydrogenation catalyst to give 2-methyl-1,5-pentanediamine in 80% yield.[12]

Hydrierung von 2-Methylenglutaronitril zu 2-Methyl-1,5-pentandiamin

Hydrogenation of 2-methylene glutaronitrile in the presence of ammonia with manganese-containing sodium oxide-doped cobalt catalyst (at 80 to 100 °C and pressures of 200 atm in a tubular reactor) leads to the addition of ammonia to the double bond and directly converts the compound to 2-aminomethyl-1,5-pentanediamine with yields of 66%.[13]

Bildung von 2-Aminomethyl-1,5-pentandiamin

The branched triamine can be used in epoxides and polyurethanes.

2-Methylenglutaronitrile reacts with methanamide upon catalysis with 4-(dimethylamino)-pyridine (DMAP) at 60 °C in 47% yield to give 1-(N-methanoylamino)-2,4-dicyanobutane, from which α- aminomethylglutaric acid is formed by subsequent hydrolysis.[14]

Reaktion von 2-Methylenglutaronitril mit Formamid zu 1-(N-Formylamino)-2,4-dicyanobutan

Heating 2-methyleneglutaronitrile with an alkaline ion exchanger, pyridine and water to 150 °C in an autoclave yields the lactam 5-cyano-2-piperidone in 80% yield.[15]

Lactambildung zum 5-Cyano-2-piperidon

2-Methylene glutaronitrile can be polymerized to various homo- and copolymers via anionic polymerization with sodium cyanide, sodium in liquid ammonia or with butyllithium. However, the polymers are formed only in low yields and show unsatisfactory properties such as intrinsic viscosities and poor mechanical properties.[16]

The main use of 2-methyleneglutaronitrile is as starting material for the broad-spectrum biocide 2-bromo-2-(bromomethyl)pentanedinitrile (methyldibromo-glutaronitrile),[17] which is formed in virtually quantitative yield by the addition of bromine to the double bond.[18]

Bromierung von 2-Methylenglutaronitril

From the chlorine-analogous 2-chloro-2-(chloromethyl)pentenenitrile, 3-cyanopyridine is obtained by heating to 150 °C with tin(IV)chloride.[17]

Bildung von 3-Cyanpyridin aus 2-Methylenglutaronitril

References

  1. ↑ "2-Methyleneglutaronitrile 1572-52-7 | TCI America" (in en). http://www.tcichemicals.com/eshop/en/us/commodity/M0222/. 
  2. ↑ Sigma-Aldrich Co., product no. 125547.
  3. ↑ L. Yu (2014), "Practical and scalable preparation of 2-methyleneglutaronitrile via an efficient and highly selective head-to-tail dimerization of acrylonitrile catalysed by low-loading of tricyclohexylphosphine", RSC Adv. 4 (37): 19122–19126, doi:10.1039/C4RA02810D 
  4. ↑ 4.0 4.1 "Production of 2-methylene-glutaronitrile" US patent 3733351, published 1973-05-15
  5. ↑ "Process for production of 2-methyleneglutaronitrile" US patent 4422981, published 1983-12-27
  6. ↑ "Dimerization method" US patent 3956358, published 1976-05-11
  7. ↑ M.M. Baizer; J.D. Anderson (1965), "Electrolytic reductive coupling. VII. A new class of acrylonitrile oligomers", J. Org. Chem. 30 (5): 1351–1356, doi:10.1021/jo01016a003 
  8. ↑ 8.0 8.1 M.M. Baizer; J.D. Anderson (1965), "Electrolytic reductive coupling. VIII. Utilization and a new preparation of α-methyleneglutaronitrile", J. Org. Chem. 30 (5): 1357–1360, doi:10.1021/jo01016a004 
  9. ↑ D. Basavaiah; V.V.L. Gowriswari; T.K. Barathi (1987), "DABCO catalyzed dimerization of α, β-unsaturated ketones and nitriles", Tetrahedron Lett. 28 (39): 4591–4592, doi:10.1016/S0040-4039(00)96573-0 
  10. ↑ "Preparation of cyano compounds" US patent 3795694, published 1974-03-05
  11. ↑ "Process for preparing aminoalkanenitriles" US patent 3350439, published 1967-10-31
  12. ↑ "Methyl pentamethylene diamine process" US patent 3408397, published 1967-10-31
  13. ↑ "Verfahren zur Herstellung von 2-Aminomethyl-1,5-pentandiamin" EP patent 1028104, published 2000-08-16
  14. ↑ "1-(N-Formylamino)-2,4-dicyanobutan und ein Verfahren zu dessen Herstellung" EP patent 0336185, published 1989-10-11
  15. ↑ "Selective hydrolysis and cyclization of unsaturated nitriles" US patent 3666766, published 1972-05-30
  16. ↑ "Process for polymerizing 2-methylene glutaronitrile" US patent 3451977, published 1969-06-24
  17. ↑ 17.0 17.1 "Preparation of 3-cyanopyridine" US patent 3644380, published 1972-02-22
  18. ↑ "Method for preparing 2-bromo-2-bromomethyl-glutaronitrile" US patent 3929858, published 1975-12-30



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