AbstractsChemistry

As part of a continuing study of sulfur containing non-aqueous solvents, the present investigation was undertaken in an effort to obtain a better understanding of the solvent sulfuryl chloride. The primary object of the investigation involved a study of the rate of radiochlorine exchange between sulfuryl and thionyl chloride in mixtures of the two, the radioisotopic tracer chlorine-36 being used. The principal motivation for such experiments rested in the hope of being able to find some evidence relative to the possible significance of an ionic dissociation process for sulfuryl chloride. The system was of particular interest in presenting analogies to at least two related types of systems previously studied, namely the thionyl chloride-thionyl bromide system (where rapid radiosulfur exchange was observed) and the thionyl chloride-sulfur monochloride system (where negligible radiochlorine exchange occurred). The system was further of interest in the light of the previous observation of a rapid chlorine exchange between sulfuryl chloride and the solute pyridinium chloride (in chloroform solution). Another point of some pertinence related to the fact that earlier research had shown that, between these two substances, little if any radiosulfur exchange occurred, and the suggestion had been made that a rapid radiochlorine exchange might result if the two substances interacted in an acid-base type of ionization equilibrium, thionyl chloride acting as a basic, chloride ion donor. It was found in this work that radiochlorine exchange between thionyl chloride and sulfuryl chloride was, at best, very slow, with an exchange half time, t1/2, of at least 35 days or more. The rate of the exchange did not appear to vary greatly, at least in apparent order of magnitude, over the concentration range from a five fold excess of sulfuryl chloride to a two fold excess of thionyl chloride, the value of the order of magnitude at 25°C being 10⁻¹ g-atoms 1⁻¹day⁻¹. The obtaining of precise rate data was, however, hampered both by the extreme slowness of the reaction and by the considerable difficulty in a clean cut reactant separation at the end of each experiment, a factor which resulted in a large and rather irreproducible apparent zero time exchange. A single experiment was done investigating the radiochloride exchange between sulfuryl chloride and the initially labeled solute tetramethylammonium chloride. Despite incomplete solution of the salt in the solvent, 84% exchange occurred in the time of the experiment (14.75 hours). It appears most likely that, if solution had been complete, exchange would also have been complete within the period of the experiment, and in all probability in a far shorter time, probably less than an hour. The results are taken to imply that sulfuryl chloride neither undergoes any significant chloride ion dissociation, nor any acid-base ionic interaction with thionyl chloride. They further suggest that exchange of the solvent with ionic chloride solutes probably occurs…