Synthesis of benzenepolythiols and their reactions with elemental sulfur.

摘要

The overall objective of this research was to examine the reaction of benzenepolythiols with elemental sulfur to determine the properties of the resultant polysulfides and their effect on the physical properties of elemental sulfur.;Benzenepolythiols are not readily accessible on a large scale, but have been prepared by nucleophilic substitution of chlorobenzene under forcing conditions. Consequently, a new method for C-S bond formation in aromatic substrates was developed using dimethyl disulfide activated by acidic mesoporous clays. This method worked well for alkylbenzenes affording a variety of methylthiolated benzene derivatives. Birch reduction of these compounds gave the desired benzenethiols in good yields.;It was found that benzene di- and trithiols reacted rapidly with liquid sulfur forming linear and network polymers respectively. Even when present in low concentrations (10-3 molar fraction), the polysulfides had significant effects on the physical properties of sulfur causing increased viscosity and a very substantial depression of freezing point (>50°C). This last effect is of considerable industrial importance as it could be applied to mitigate sulfur deposition in natural gas wells and pipelines and allow transport of liquid sulfur at a low cost.;Linear and network polysulfides were also prepared in organic solvent solution. Elemental and Raman spectroscopic analysis indicated that, on average, sulfur couplings between aromatic units consisted of tri- and tetrasulfide linkages. Polysulfides isolated from liquid sulfur were elastomeric in nature but were unstable and were contaminated with polymeric sulfur.