STUDIES IN ORGANIC ELECTROCHEMISTRY (IODOOCTANE, BROMOOCTANE)

Pulse polarograms for 2-iodooctane in dimethylformamide containing 0.1 F tetraalkylammonium perchlorate exhibit two waves of equal height, attributed to stepwise reduction to the sec-octyl radical and carbanion, respectively, whereas 2-bromooctane gives a single two-electron pulse polarographic wave, the height of which is equal to the sum of the two waves for the alkyl iodide. Large-scale controlled-potential electrolyses of 2-iodooctane at potentials corresponding to the first pulse polarographic wave result in mercury-stabilized sec-octyl radicals which can disproportionate to yield octane along with 1-octene and 2-octene, can couple to give the dimeric species (7,8-dimethyltetradecane), or can interact with mercury to afford di-sec-octylmercury. Carbanion-derived products are obtained when the alkyl iodide is electrolyzed at potentials on the second wave.;Electrochemical reduction of diphenyliodonium salts and phenylmercuric halides in dimethylformamide containing tetramethylammonium perchlorate has been studied with the aid of polarography and coulometry. The number of polarographic waves was found to be sensitive to the concentration of both the supporting electrolyte and starting material. A mechanism has been proposed to account for all the experimental observations and the uptake of four electrons. Cyclic voltammetric experiments with platinum electrodes were used to support the proposed mechanism.;The effect of substituents on the electrochemistry of diphenyliodonium salts has been investigated. A number of unsymmetrically substituted diphenyliodonium bromides has been synthesized and their electrochemistry has been studied by means of polarography and coulometry. Substituents have no effect on the half-wave potential of the first polarographic wave for these compounds, but the half-wave potential of the second wave (which corresponds to reduction of substituted iodobenzene, one of the electrolysis products) is shifted toward more positive values as the electron-withdrawing power of the substituent increases. Interestingly, substituents do affect the product distribution obtained from electrolyses done at potentials corresponding to the first wave. A mechanism is proposed to account for these observations.;To complement the preceding work, a study of the electrochemistry of secondary alkyl halides at carbon has been undertaken. Cyclic voltamograms for 2-iodooctane at glassy carbon exhibit two irreversible waves. Large-scale electrolyses at reticulated vitreous carbon indicate that 2-iodooctane undergoes stepwise reduction to the sec-octyl radical and carbanion, respectively. On the other hand, 2-bromooctane undergoes a one-step reduction to the carbanion as shown by cyclic voltammetry and coulometry.