Contributions to the chemistry of disulfur monoxide

Abstract

Disulfur monoxide is an unstable gaseous species. Even at comparatively lower temperatures, it undergoes decomposition into sulfur dioxide and elemental sulfur. When dissolved in chilled carbon tetrachloride, the solution remains stable for a few hours. In the past, attempts have been made to stabilize it chemically by binding it with reagents such as trimethylamine. Hydroquinone is known to form clathrate compounds with several guest molecules, including sulfur dioxide, hydrogen sulfide, methyl alcohol, hydrogen chloride, and inert gases. The host crystal of hydroquinone that accommodates guest molecules (?-hydroquinone) can be distinguished from the crystals of hydroquinone without guest molecules (?-hydroquinone). Since the molecular parameters of disulfur monoxide closely resemble those of sulfur dioxide, it is reasonable to expect the formation of a clathrate of hydroquinone with disulfur monoxide. The present work attempts to prepare the clathrate compound of hydroquinone with disulfur monoxide and characterize its nature.

Preparation of Disulfur Monoxide Clathrate

Disulfur monoxide solution is prepared by passing the products of combustion of sulfur in oxygen at 57 mm Hg through chilled carbon tetrachloride (-18°C). Sulfur dioxide dissolved in carbon tetrachloride is expelled by continuous evacuation. A 50% solution of hydroquinone in n-propyl alcohol is added dropwise to the chilled disulfur monoxide solution. Clathrate crystals separate out, which are then:

Washed thoroughly with cold carbon tetrachloride Dried in vacuum

Chemical Analysis

The clathrate crystals contain 47% sulfur, present in the form of disulfur monoxide. This is confirmed by:

Reduction with anhydrous hydrogen iodide, converting sulfur to hydrogen sulfide, which is isolated and estimated. Alkali hydrolysis in the presence of cadmium hydroxide, yielding cadmium sulfide.

These evidences confirm the presence of disulfur monoxide in the hydroquinone clathrate compound.

Physico-Chemical Characterization

Morphology: Host crystals of hydroquinone differ from clathrate crystals. For comparison, morphologies of ?-hydroquinone and clathrates of sulfur dioxide and hydrogen sulfide (?-hydroquinone) are described. X-ray Powder Diffraction:

Disulfur monoxide clathrate pattern compares favorably with sulfur dioxide and hydrogen sulfide clathrates. Diffraction pattern of ?-hydroquinone differs in three interplanar spacings from clathrates.

Infrared Spectroscopy:

IR spectrum of ?-hydroquinone differs from that of ?-hydroquinone. Guest species cannot be identified by IR, but differences confirm clathrate formation.

Thermal Analysis:

Differential thermal analysis shows three endothermic peaks between 40°C and 300°C, similar to clathrates of sulfur dioxide and methyl alcohol.

Conclusion It is thus possible to stabilize disulfur monoxide by forming a clathrate complex with hydroquinone, similar to clathrates of sulfur dioxide.