2-Methylglutaronitrile

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2-Methylglutaronitrile
File:2-Methylglutaronitril Struktur.svg
Names
Preferred IUPAC name
2-Methylpentanedinitrile
Other names
1,3-Dicyanobutane, α-Methylvalerodinitrile
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 224-923-5
MeSH C480967
UNII
  • InChI=1S/C6H8N2/c1-6(5-8)3-2-4-7/h6H,2-3H2,1H3
    Key: FPPLREPCQJZDAQ-UHFFFAOYSA-N
  • CC(CCC#N)C#N
Properties
C6H8N2
Molar mass 108.144 g·mol−1
Appearance colorless liquid
Density 0.9548 g/cm3
Melting point −45 °C (−49 °F; 228 K)
Boiling point 263 °C (505 °F; 536 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

2-Methylglutaronitrile is the organic compound with the formula NCCH2CH2CH(CH3)CN. This dinitrile is obtained in the large-scale synthesis of adiponitrile. It is a colorless liquid with an unpleasant odor. It is the starting compound for the vitamin nicotinamide and for the diester dimethyl-2-methylglutarate and the ester amide methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate, which are promoted as green solvents. 2-Methylglutaronitrile is chiral but is mainly encountered as the racemate. It is also used to make Dytek A.[1]

Occurrence and production

2-Methylglutaronitrile is a by-product of the production of adiponitrile, the precursor of hexamethylenediamine and adipic acid as building blocks for nylon 66. Starting from 1,3-butadiene or a butadiene-rich C4-section (> 40% by volume) from a naphtha steamcracker in the first stage a mixture of pentenenitriles is obtained through hydrocyanation (using as catalyst Ni0-phosphine [PR3][2] or phosphite or phosphonite [P(OR)2R][3]). The mixture contains mainly trans-3-pentenenitrile in addition to the isomers 2-methyl-2-butenenitrile, 4-pentenenitrile and 2-pentenenitrile.

1,3-Butsdien zu Pentennitrilen
1,3-Butsdien zu Pentennitrilen

The mixture of monoolefinic C5 mononitriles is isomerized to 3- and 4-pentenenitrile with a hydrocyanation catalyst and a Lewis acid (such as ZnCl2).[3] In the third step, the mixture is reacted with hydrogen cyanide to give a mixture of dinitriles which contains in addition to 2-methylglutaronitrile also adiponitrile and 2-ethylbutanedinitrile.

Umsetzung von Pentennitrilen zu Dinitrilen
Umsetzung von Pentennitrilen zu Dinitrilen

2-Methylglutaronitrile can be separated by fractional distillation.[4] The 2-methylglutaronitrile-rich fraction has hitherto been combusted as an undesired by-product of adiponitrile production, having the typical composition of about 86 wt% 2-methylglutaronitrile, 11 wt% 2-succinonitrile and 3 wt% adiponitrile.[5][6]

Applications

2-methylglutaronitrile can be converted to 3-methylpyridine (β-picoline) by partial hydrogenation.[7][8]

3-Methylpyridin aus 2-MGN
3-Methylpyridin aus 2-MGN

In addition to 3-methylpyridine, 3-methylpiperidine is obtained as a by-product from which further 3-methylpyridine can be obtained by dehydrogenation. Ammonoxidation of 3-methylpyridine on transition metal contacts yields 3-cyanopyridine (nicotinonitrile) in yields of 95%.[9]

Nicotinsäureamid aus 3-Methylpyridin
Nicotinsäureamid aus 3-Methylpyridin

Hydrogenation of a solution of 2-methylglutaronitrile in ethanol in the presence of Raney cobalt at 15 bar and 100 °C yields 2-methylpentane-1,5-diamine.[10]

2-Methylpentan-1,5-diamin aus 2-Methylglutaronitril
2-Methylpentan-1,5-diamin aus 2-Methylglutaronitril

2-Methylpentanediamine can be converted to 3-methylpiperidine at 300 to 400 °C on a zeolite contact and then dehydrated on a palladium contact to 3-methylpyridine, which can be converted via nicotinonitrile into nicotinamide.[11] The racemic diamine can also be used for the preparation of specific polyamides and after reaction with phosgene to form 2-methylpentane diisocyanate[12] as a reaction component in polyurethanes. Nitrilases regioselectively hydrolyze the ω-nitrile group in α, ω-dinitriles without detectable amide intermediate directly to the carboxyl group. 4-cyanopentanoic acid is formed in high yield.[13]

4-Cyanopentansäure aus 2-Methylglutaronitril
4-Cyanopentansäure aus 2-Methylglutaronitril

The ammonium salt of 4-cyanopentanoic acid can be converted by catalytic hydrogenation in the presence of methylamine in 1,5-dimethyl-2-piperidone,[14][15] an environmentally compatible solvent.[16]

Synthese von 1,5-Dimethyl-2-piperidon
Synthese von 1,5-Dimethyl-2-piperidon

The hydrolysis of both nitrile groups of 2-methylglutaronitrile with e.g. 20% sodium hydroxide solution at 50 °C and subsequent acidification produces 2-methylglutaric acid.[17]

2-Methylglutarsäure aus 2-Methylglutraronitril
2-Methylglutarsäure aus 2-Methylglutraronitril

Starting from 2-methylglutaronitrile the hydrolysis to 2-methylglutaric acid can also be accomplished via the 2-methylglutarimide obtained by heating a 2-methylglutaronitrile/water mixture to 275 °C in the presence of a titanium dioxide catalyst in yields of 94%.[18]

2-MGN-Imid aus 2-Methylglutaronitril
2-MGN-Imid aus 2-Methylglutaronitril

Hydrolysis in the alkaline provides 2-methyl glutaric acid. The reaction of 2-methylglutarimide with e.g. methanol (methanolysis) produces the diester dimethyl-2-methylglutarate[19] in the presence of titanium dioxide[5] or lanthanum oxide.[20] It was commercialized as an environmentally friendly aprotic dipolar solvent under the name Rhodiasolv IRIS with the typical composition 87-89% dimethyl-2-methylglutarate, 9-11% dimethyl 2-ethylbutanedioate and 1-2% dimethyl hexanedioate[6] as a substitute for acetone, dichloromethane, N-methylpyrrolidone and the like.

Diester aus 2-MGN-Imid
Diester aus 2-MGN-Imid

The ester mixture is very similar to so-called dibasic esters, which are commercially available as FlexiSolv DBE esters.[21] The diester can be selectively converted into a mixture of 1- or 5-substituted methyl ester amides with dimethylamine in methanol/sodium methoxide,[22] which is used under the name Rhodiasolv Polarclean as formulation auxiliaries for crop protection preparations.[6] The resulting ester amides are readily biodegradable and good solvents for a variety of different plant protection agents (such as insecticides or fungicides), also compared to the frequently used N-methylpyrrolidone, cyclohexanone or isophorone. Other esteramides are derived, e. g. from 2-methylglutaronitrile which, after alkaline hydrolysis, is converted into 2-methylglutaric acid, cyclized with acetic anhydride to give 2-methylglutaric anhydride, reacted with dimethylamine to form the monoamide, reacted to an acid chloride with thionyl chloride and formed to an ester with more hydrophobic alcohols (like butanols or cyclohexanol).[23]

References

  1. Eller, Karsten; Henkes, Erhard; Rossbacher, Roland; Höke, Hartmut (15 June 2000). "Amines, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a02_001. ISBN 3527306730.
  2. US 5856555, M. Huser, R. Perron, "Process for the hydrocyanation of organic compounds containing ethylenic unsaturation", published 1999-01-05, assigned to Rhone-Poulenc Fiber & Resin Intermediates 
  3. 3.0 3.1 US 6242633, J. Fischer, W. Siegel, "Catalyst comprising at least one phosphonite ligand based Nickel (0) complex and method for the production of nitriles", published 2001-06-05, assigned to BASF AG 
  4. US 7816551, T. Jungkamp, R. Baumann, M. Bartsch, G. Haderlein, H. Luyken, J. Scheidel, "Method for producing dinitriles", published 2010-10-19, assigned to BASF AG 
  5. 5.0 5.1 US 8053594, P. Leconte, P. Marion, R. Jacquot, "Preparation of diesters from imide/dinitrile compounds", published 2011-11-08, assigned to Rhodia Operations 
  6. 6.0 6.1 6.2 Vidal, T. (14 June 2012). "Sustainable Solvents Products and Process Innovations" (PDF). Archived from the original (PDF) on 2016-05-12. Retrieved 2016-04-28.
  7. CH 654576, E.J. Newson, T.-B. Truong, "Verfahren zur Herstellung von 3-Methylpyridin", published 1986-02-28, assigned to Lonza AG 
  8. US 4876348, R. DiCosimo, J.D. Burrington, D.D. Suresh, "Process for making 3-cyanopyridine", published 1989-10-24, assigned to The Standard Oil Co. 
  9. Abe, Nobuyuki; Ichimura, Hisao; Kataoka, Toshiaki; Morishita, Sinji; Shimizu, Shinkichi; Shoji, Takayuki; Watanabe, Nanao (2007). "Pyridine and Pyridine Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_399. ISBN 978-3527306732.
  10. US 4987263, G. Cordier, "Preparation of 2-methylpentadiamine", published 1991-01-22, assigned to Rhone-Poulenc Chimie 
  11. US 5719045, J. Heveling, E. Armbruster, L. Utiker, M. Rohner, H.-R. Dettwiler, R.J. Chuck, "Process for preparing nicotinamide", published 1998-02-17, assigned to Lonza AG 
  12. WO 2008074645, P. Pfab, E. Ströfer, C. Knösche, E. Schwab, M. Klötzer, G. Georgi, "Process for preparing 2-methylpentane-1,5-diisocyanate from methylglutaronitrile", published 2008-06-26, assigned to BASF SE 
  13. US 6551804, R. DiCosimo, R.D. Fallon, J.E. Gavagan, "Process for preparing 4-cyanopentanoic acid", published 2003-04-22, assigned to E.I. Du Pont de Nemours and Co. 
  14. US 5814508, R. DiCosimo, R.D. Fallon, J.E. Gavagan, F.E. Herkes, "Preparation of lactams from aliphatic α, ω-dinitriles", published 1998-09-29, assigned to E.I. Du Pont de Nemours and Co. 
  15. F.B. Cooling; et al. (2001). "Chemoenzymatic production of 1,5-dimethyl-2-piperidone". Journal of Molecular Catalysis B: Enzymatic. 11 (4–6): 295–306. doi:10.1016/S1381-1177(00)00150-8.
  16. US 6261381, G. Wojcik, "Composition and process for cleaning inks from various substrates including printing plates", published 2001-07-17, assigned to MacDermid, Inc. 
  17. INVISTA, Technical Information, DYTEK Methylglutaronitrile (MGN)
  18. US 20150175515, R. Jacquot, B. Rhers, "Process for preparing diacid compounds", published 2015-06-25, assigned to Rhodia Operations 
  19. Solvay: GPS Safety Summary, Dimethyl 2-methylglutarate Archived 2014-08-05 at the Wayback Machine
  20. US 20120071686, R. Jacquot, P. Leconte, "Production of diesters from dinitrile compounds", published 2012-03-22 
  21. INVISTA's DBE esters, FlexiSolv DBE esters Archived 2016-11-16 at the Wayback Machine
  22. US 20130237722, T. Vidal, R. Rached, M. Guglieri, "Process for preparing esteramide compounds", published 2013-09-12, assigned to Rhodia Operations 
  23. US 20140221211, O. Jentzer, M. Guglieri, "Use of esteramides as solvents, novel esteramides and process for preparing esteramides", published 2014-08-07, assigned to Rhodia Operations