Modern Routes
The majority of adiponitrile is prepared by the nickel-catalysed hydrocyanation of butadiene, as discovered at duPont. The net reaction is:
- CH2=CHCH=CH2 + 2 HCN → NCCH2CH2CH2CH2CN
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.
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 electrosynthesis, starting from acrylonitrile, which is dimerized:
- 2 CH2=CHCN + 2 e- + 2 H+ → NCCH2CH2CH2CH2CN
The electrolytic coupling of acrylonitrile was discovered at Monsanto Company.
Read more about this topic: Adiponitrile, Production
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