Acrylonitrile, electroreduction

Feoktistov, L. G., A. P. Tomilov, and 1. G. Sevast Yanova. Relation between the acrylonitrile electroreduction products and the proton donating properties of the solution. 

A.sahi Chemical EHD Processes. In the late 1960s, Asahi Chemical Industries in Japan developed an alternative electrolyte system for the electroreductive coupling of acrylonitrile. The catholyte in the Asahi divided cell process consisted of an emulsion of acrylonitrile and electrolysis products in a 10% aqueous solution of tetraethyl ammonium sulfate. The concentration of acrylonitrile in the aqueous phase for the original Monsanto process was 15—20 wt %, but the Asahi process uses only about 2 wt %. Asahi claims simpler separation and purification of the adiponitrile from the catholyte. A cation-exchange membrane is employed with dilute sulfuric acid in the anode compartment. The cathode is lead containing 6% antimony, and the anode is the same alloy but also contains 0.7% silver (45). The current efficiency is of 88—89%, with an adiponitrile selectivity of 91%. This process, started by Asahi in 1971, at Nobeoka City, Japan, is also operated by the RhcJ)ne Poulenc subsidiary, Rhodia, in Bra2il under Hcense from Asahi. 

Applications As the basic process of electron transfer at an electrode is a fundamental electrochemical principle, polarography can widely be applied. Polarography can be used to determine electroreductible substances such as monomers, organic peroxides, accelerators and antioxidants in solvent extracts of polymers. Residual amounts of monomers remain in manufactured batches of (co)polymers. For food-packaging applications, it is necessary to ensure that the content of such monomers is below regulated level. Polarography has been used for a variety of monomers (styrene, a-methylstyrene, acrylic acid, acrylamide, acrylonitrile, methylmethacrylate) in... 

Asami R, Atobe M, Fuchigami T (2006) Ultrasonic effects on electroorganic processes. Part 27. Electroreduction of acrylonitrile at suspended lead particle-electrode. Ultrason Sonochem 13 19-23, and the series... 

Vitamin B12 derivatives are also effective catalysts for the electroreductive cyclization of bromoalkenes in conductive microemulsions,299 300 or for ring-expansion reactions in cyclic a-(bromomethyl)-(3-keto esters in DMF.301 Vitamin Bi2 attached to an epoxy-polymer has been used in electrosynthesis of valeronitrile by reductive coupling of iodoethane and acrylonitrile.302... 

These latter workers liave demonstrated, by electrochemical experiments, the different reactivities of 125 and its cis isomer.Thus, whereas 125 is formed essentially reversibly and lost in a slow dimerization reaction and a slow coupling with unreduced thioindigo, its cis isomer is rapidly consumed in isomerization, radical-radical, and radical-parent coupling reactions. Similar differential reactivities with carbon dioxide, acrylonitrile, and cin-namonitrile were also observed. For 6,6 -diethoxytliioindigo, it was found that the electroreduction of the cis and trans isomers occurred at different... 

To illustrate this technique, consider the dimerization of the acrylonitrile anion radical (AN") in DMF (26). The electroreductive hydrodimerization of AN is used commercially to produce adiponitrile [(ANH)2], a precursor in Nylon production. The proposed reaction mechanism, an E1.C2 reaction [Section 12.1.1(b)], is... 

It has been shown by studies of the electroreduction of acrylonitrile at Pb, Ni, and Pt cathodes in the presence of quaternary ammonium salts that the yield of adiponitrile depends on the electrode material, with little dependence on cathode potential. On a Pb cathode the yield of adiponitrile was found to be almost independent of quaternary ammonium salt concentration, whilst on a Ni cathode the yield increased with increasing concentration of quaternary salt. The yield of adiponitrile, when a Pt cathode was used, was low and this led to the conclusion that atomic H2 plays a part in the mechanism. The ratio V2/v (dimerization/propionitrile rates) from their common... 

Vinylic monomers such as acrylonitrile (AN) or methacrylonitrile (MAN) undergo an electropolymerization when submitted to electroreduction at metallic cathodes in an anhydrous organic medium [1,2], This synthesis leads to two different kinds of products (i) a physisorbed polymer which can be removed by rinsing with an appropriate solvent and (ii) a so-called grafted polymer, which is not removed with a solvent, even under sonication, and bearing carbon/metal interface chemical bonds which have been identified by X-ray Photoelectron Spectroscopy [2] and EXES [3], The former can be up to several micrometers thick, whereas the latter has a thickness which never exceeds a few hundreds Angstroms. 

However, the most significant changes in nylon-6, 6 production lie in the newer routes to adiponitrile introduced by Monsanto and Du Pont into both the U.S.A. and Western Europe. The former entails the electroreductive dimerization of acrylonitrile, while Du Pont use the addition of HCN to 1,3-butadiene catalysed by Ni(0) complexes ... 

It might appear likely that electroreduction processes take place directly by electronst on metals which have high hydrogen overpotential and by H(a) on low overpotential metals. Indeed, e.g., electroreduction of acrylonitrile to adiponitrile on Pb or Hg takes place by electronation, followed by proton addition and dimerization, while electrolytic olefin hydrogenation on Pt takes place by transfer of H(a) to the organics. Nevertheless, such... 

Again the dimerization or coupling reactions will involve free radicals or radical ions, but the intermediates are generated cathodically. Suitable substrates are electrophiles such as activated olefins and carbonyl compounds. In this section, it is intended to focus only upon the electroreduction of activated olefins, partly because the electrode reactions of aldehydes and ketones has been discussed earlier. However, it is the electrohydrodimerization of an activated olefin that has become a successful, commercial electro-organic process, i.e., the electroreduction of acrylonitrile developed by Monsanto ... 

It is obtained commercially by the electroreductive coupling of acrylonitrile. By this process about 90% of adiponitrile is obtained. In this process a concentrated solution of certain quaternary ammonium salts (QASs), such as... 

Electrosynthesis is a quite unique tool for synthesis of fine chemicals, wherein highly selective, efficient, and/or environmental benign reactions are performed without use of any oxidizing and reducing reagents under atmospheric conditions. Many successful applications have been accumulated so far [1—3], and some electrosyntheses of useful chemicals in an industrial scale, such as electroreductive coupling acrylonitrile leading to adiponitrile, have been realized [4]. 

Figm 6 Proposal of mechanism for the electroreduction of acrylonitrile at the potentials of peak I and peak II, respectively. 

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