Direct Reduction of Alkyl Monohalides at Silver in Dimethylformamide: Effects of Position and Identity of the Halogen

Abstract

AbstractElectrochemical reduction of primary (1‐halodecane), secondary (2‐halohexane and cyclohexyl halide), and tertiary halides (tert‐butyl halide) at a silver cathode in dimethylformamide (DMF) containing 0.050 M tetramethylammonium perchlorate (TMAP) was investigated with the aid of cyclic voltammetry and controlled‐potential (bulk) electrolysis for iodides, bromides, and chlorides. Selected reductions were probed in dried DMF–TMAP and DMF containing tetra‐n‐hexylammonium perchlorate (THAP). Cyclic voltammograms reveal that the number of cathodic peaks and their potentials are highly dependent on the identity and position of the halogen as well as the composition of the solvent–electrolyte. Intermediates arising from bulk electrolysis of these halides at silver undergo both radical and carbanion reactions. Electrolysis products depend on the identity and position of the halogen, amount of residual water, and size of the electrolyte cation in the solvent–electrolyte. Theoretical calculations of molecular dipole moments and polarizabilities were performed and compared to experimental observations.