Electro-hydrodimerization

Dir, whereas for small distances d < r), /r Did. The large effective obtainable enables fast heterogeneous reaction rates to be measured under steady-state conditions. Zhou and Bard measured a rate constant of 6 x 10 Ms for the electro-hydrodimerization of acrylonitrile (AN) and observed the short-lived intennediate AN for this process [65]. 

In 2000, about 110 chemicals were being produced by electro-organic syntheses at a rate of more than 10,000 tons/year. The best-known method has already been presented in this chapter (Section 11.2.3) it is the electro-hydrodimerization of acrylonitrile to adiponitrile as part of the synthesis of nylon. 

The ammoxidation process ( eq. 8 ) displaced the more expensive acetylene-HCN-based route in the early 1960 s (eq. 20). Other obsolete processes also involve more expensive reagents (e.g. ethylene oxide, eq. 19, and acetaldehyde, eq. 21) and oxidants (e.g. NO, eq. 22). The impact of the introduction of the ammoxidation process in 1960 was an immediate drastic reduction in acrylonitrile price and greatly increased production which made possible many of today s high-volume applications of acrylonitrile (Figure 6A). The production of acrylonitrile, which accounts for 17% of the total U. S. propylene consumption, is used extensively in fibers, plastics and resins (ARS/SA) and rubber industries, with a growing number of miscellaneous applications, including the electro-hydrodimerization process for adiponitrile production (Figure 6B). 

Various diphenylethylenes are reduced in high yield by magnesium in methanol. Expectedly, reductions of conjugated double bonds via one-electron transfer processes can also be carried out electro-chemically. Scheme 87 illustrates both the reduction of a conjugated alkene and partial trapping of the intermediate anion radical to yield a mixed hydrodimerization product. 

With 3-methylcinnamonitrile (entry 2), hydrodimerization was the main pathway followed, whereas acrylonitrile (entry 3) afforded the best yields of cyanomethylated product under conditions similar to those observed for cinnamonitrile. Efforts to accomplish the Michael addition of CH2CN to acrylonitrile, with the anionic reagent obtained via deprotonation of MeCN by electro reduced azobenzene (entry 4), gave glutaronitrile in low yields but no adiponitrile (hydrodimerization product). Anionic polymerization of acrylonitrile was the main reaction pathway. 

Conjugated Alkenes. - By far the largest and best known industrial electro-organic reduction is the hydrodimerization of acrylonitrile to adiponitrile, an important precursor in nylon manufacture. Plants where this process... 

---