Effect of alkyl chain length on the aqueous solubility and redox properties of symmetrical dixanthogens

Abstract

Aqueous solubilities of methyl, ethyl and propyl dixanthogens have been determined spectrophoto-metrically. The dependence of solubility on alkyl chain length is interpreted in terms of the hydrophobic effect with dixanthogen molecules being 'folded' in aqueous solution. The solubilities of butyl and pentyl dixanthogens were estimated by extrapolation of the data for the lower homologues. Knowledge of dixanthogen solubilities allows calculation of Eº values for dixanthogen/xanthate systems referred to 1 M solutions as standard states from published values referred to saturated dixanthogen solutions. The variation in Eº values with chain length is due to both an electronic effect and the conformation of dixanthogen in solution. These conclusions are supported by Eº values measured in an acetone/water solvent in which dixanthogen as well as xanthate solutions of known concentration can be prepared.