Adiponitrile

Adiponitrile is the organic compound with the formula (CH2)4(CN)2. This dinitrile, a viscous, colourless liquid, is an important precursor to the polymer nylon-6,6. In 2005, about one million tonnes were produced.[4]

Adiponitrile
Names
IUPAC name
Hexanedinitrile[1]
Other names
  • Adipic acid dinitrile
  • Adipic acid nitrile
  • Adipyldinitrile
  • 1,4-Dicyanobutane
  • Hexanedioic acid dinitrile
  • Nitrile adipico
  • Tetramethylene cyanide
  • Tetramethylene dicyanide
Identifiers
3D model (JSmol)
1740005
ChemSpider
ECHA InfoCard 100.003.543
EC Number
  • 203-896-3
MeSH adiponitrile
RTECS number
  • AV2625000
UNII
UN number 2205
Properties
C6H8N2
Molar mass 108.144 g·mol−1
Appearance Colourless liquid
Density 951 mg mL−1
Melting point 1 to 3 °C; 34 to 37 °F; 274 to 276 K
Boiling point 295.1 °C; 563.1 °F; 568.2 K
50 g/L (20 °C)
Vapor pressure 300 mPa (at 20 °C)
1.438
Thermochemistry
Std enthalpy of
formation (ΔfH⦵298)
 84.5–85.3 kJ mol−1
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H301, H315, H319, H330, H335
P260, P284, P301+310, P305+351+338, P310
NFPA 704 (fire diamond)
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
3
0
Flash point 93 °C; 199 °F; 366 K (open cup)[2]
550 °C (1,022 °F; 823 K)
Explosive limits 1.7–4.99%
Lethal dose or concentration (LD, LC):
155 mg kg−1 (oral, rat)
NIOSH (US health exposure limits):
PEL (Permissible)
 none[2]
REL (Recommended)
 TWA 4 ppm (18 mg/m3)[2]
IDLH (Immediate danger)
 N.D.[2]
Related compounds
Related alkanenitriles
 Glutaronitrile
Related compounds
 hexanedioic acid
hexanedihydrazide
hexanedioyl dichloride
hexanediamide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Production

Early routes

Because of the industrial value of adiponitrile, many methods have been developed for its synthesis. Early industrial routes started from furfural and later by the chlorination of butadiene to give 1,4-dichloro-2-butene, which with sodium cyanide, converts to 3-hexenedinitrile, which in turn can be hydrogenated to adiponitrile:[4]

ClCH2CH=CHCH2Cl + 2 NaCN → NCCH2CH=CHCH2CN + 2 NaCl
NCCH2CH=CHCH2CN + H2 → NC(CH2)4CN

Adiponitrile has also been produced from adipic acid, by dehydration of the diamide, but this route is rarely employed.

Modern routes

The majority of adiponitrile is prepared by the nickel-catalysed hydrocyanation of butadiene, as discovered at DuPont, pioneered by Drinkard. The net reaction is:

CH2=CHCH=CH2 + 2 HCN → NC(CH2)4CN

The process involves several stages, the first of which involves monohydrocyanation (addition of one molecule of HCN), affording isomers of pentenenitriles as well as 2- and 3-methylbutenenitriles. These unsaturated nitriles are subsequently isomerized to the 3-and 4-pentenenitriles. In the final stage, these pentenenitriles are subjected to a second hydrocyanation, in an anti-Markovnikov sense, to produce adiponitrile.[4]

Research has shown that the 3-pentenenitrile, formed in the first hydrocyanation, can undergo alkene metathesis to give dicyanobutenes, which are readily hydrogenated as described above.

The other major industrial route involves hydrodimerization, starting from acrylonitrile:[5][6]

2 CH2=CHCN + 2 e− + 2 H+ → NCCH2CH2CH2CH2CN

The electrolytic coupling of acrylonitrile was discovered at Monsanto Company.

Applications

Almost all adiponitrile is hydrogenated to 1,6-diaminohexane for the production of nylon:[7]

NC(CH2)4CN + 4 H2 → H2N(CH2)6NH2

Like other nitriles, adiponitrile is susceptible to hydrolysis. The resulting adipic acid however is more cheaply prepared by other routes.

Safety

The LD50 for adiponitrile is 300 mg/kg for oral ingestion by rats.[4]

In 1990, ACGIH adopted a time weighted average Threshold Limit Value of 2ppm for work related skin exposure.[8]

The NIOSH recommended skin exposure limit for a work related time weighted average concentration is 4ppm (18 mg/m3).[9]

It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[10]

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References
  1. "adiponitrile - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification. Retrieved 15 June 2012.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0015". National Institute for Occupational Safety and Health (NIOSH).
  3. "Archived copy". Archived from the original on 2015-04-02. Retrieved 2015-03-26.CS1 maint: archived copy as title (link)
  4. M. T. Musser, "Adipic Acid" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a01_269
  5. Cardoso, D. S.; Šljukić, B.; Santos, D. M.; Sequeira, C. A. (July 17, 2017). "Organic Electrosynthesis: From Laboratorial Practice to Industrial Applications". Organic Process Research & Development. 21 (9): 1213–1226. doi:10.1021/acs.oprd.7b00004.
  6. Baizer, Manuel M. (1964). "Electrolytic Reductive Coupling". Journal of the Electrochemical Society. 111 (2): 215. doi:10.1149/1.2426086.
  7. Robert A. Smiley "Hexamethylenediamine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a12_629
  8. 2009 TLVs and BEIs, American Conference of Governmental Industrial Hygienists, Signature Publications, page 11 of 254.
  9. NIOSH Pocket Guide NIOSH Publication 2005-149; September 2005
  10. "40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities" (PDF) (July 1, 2008 ed.). Government Printing Office. Archived from the original (PDF) on February 25, 2012. Retrieved October 29, 2011. Cite journal requires |journal= (help)
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