The electrolytic reduction and sodium reduction‐polymerization of acrylonitrile

Abstract

The reduction of acrylonitrile at mercury electrodes has been studied both polarographically and coulometrically at controlled potential. The half‐wave potential is about 1.6 v. versus a mercury pool both for pure acrylonitrile and for acrylonitrile in dimethylformamide, in the presence and absence of water. As long as water is present the diffusion current is directely proportional to the concentration of acrylonitrile, at least up to 0.2 mg./ml. In the absence of water, reduction of acrylonitrile in dimethylformamide at this potential leads to condensation of reactions initiated by the carbanion. The diffusion current is no longer proportional to the concentration. Comparison of electrolytic‐ and sodium‐reduction products of acrylonitrile gives information about the mechanisms of these reductions and the role of water in the polarographic analysis. A new yellow sodium‐reduction polymer of acrylonitrile is described, and data on the ultraviolet and infrared spectra are presented.

Electrolytic Reductive Coupling

“…If the formation of dimer products involved the dimerization of the free radicals 7, Eq. [10], an increase in the water concentration should result in an increase in dimeric products, in contrast to what is observed experimentally.…”

“…From the measured rate constants, vide infra, it is clear that the generated anion radicals 5 react with incoming depolarizer within the lifetime of the mercury drop. Under the anhydrous conditions employed here, the reaction can form trimers or higher oligomers as well as dimers, thereby exhibiting a diffusion current somewhat less than one electron per molecule (10,26). Since the dianion 7 has two negative charges in the same molecule, it would be expected to react even more rapidly with incoming depolarizers than the anion radical 5, initiating oligomerization and thereby causing the observed decrease in the limiting current at the potential of the second reduction (13).…”

“…[3]) and have not thus far resulted in a 2e 2CH~=CHCN ~ NC (CH2)4CN -t-2 OH [3] 2H20 completely satisfactory detailed elucidation of the reaction. Concerning process [2] evidence has been presented (9) in support of the proposal that concerted one-electron transfer-ring closure occurs followed by a second reduction step Now olefins 1 and 2 show only one polarographic wave; the limiting diffusion current corresponds to two or fewer electrons per molecule depending on the concentration and type of proton donor available (10). The major mechanistic problems concerning the reactions of 1 and 2 arise then from the fact that the presumed anion radical intermediate reacts with monomer, proton source, or possibly another anion radical before its presence can be verified by available instrumental methods.…”

“…Three possible reaction paths can be written for the disappearance of these anion radical intermediates 5, Eq. [10], [11], and [12]. The measured rate constants for the reaction of the anion…”

“…5 + XCH=CHY--> dimeric anion radical [11] 5 + 5 --> dimeric dianion [12] radical 5 of representative olefins, Table V, with water clearly indicate that Eq. [10] is not a major path for the reaction of the anion radicals and, therefore, for the formation of dimeric products, e.g., for olefin X, ko/kw = 105. The yield of dimeric products is, however, dependent on the concentration of water in the electrolysis mixture (9).…”