Organic Sulfur Compounds

Abstract

AbstractSulfur appears in group VI of the periodic table, just below oxygen. Similar to other second row elements, sulfur is more versatile as a reaction center than first‐row counterparts. Both oxygen and sulfur tend to alter the reactivity of an adjacent carbon atom, but sulfur itself is more reactive than oxygen toward nucleophilic, electrophilic, and radical reagents. Therefore, chemical reactions that involve organic sulfur compounds tend to occur directly at sulfur. Organic sulfur compounds are economically important in every type of industry, including manufacturing, agriculture, the environment, and pharmaceuticals. The chemicals included in this chapter were selected on the basis of their common industrial uses and commercial importance, although some compounds have multiple types of use. The chemicals have been grouped according to chemical classes. The major focus is on mercaptans (also called thiols or sulfhydryls), and sulfides, chemicals with both sulfur and oxygen atoms (sulfoxides, sulfones, sulfonates, and sulfonyl chlorides), and a miscellaneous group (thiophenes and benzothiazoles). There is a paucity of toxicological data in the open literature for many of these compounds, and a wealth of scientific information that is contained in unpublished industrial documents. Many of these unpublished reports have been referred to in previous editions of Patty's. So that the important information contained in these reports is not lost to the scientific and industrial communities, they have been maintained in the current chapter and referred to in the text, rather than in the list of references.The basic chemical and physical properties of industrially important organic sulfur compounds are summarized. The distinctive odor associated with sulfur is particularly important for many of these compounds. Often thought of as pleasant at low concentrations, higher subtoxic concentrations are often extremely offensive. The thiol containing amino acid cysteine is important in maintaining proper protein structure via disulfide bonds between two cysteine residues. In addition, cysteine forms the reactive moiety of the intracellular antioxidant glutathione that helps maintain the highly reduced state of cells and protects cells from potentially toxic electrophiles and radicals that may originate from metabolism or from foreign sources (xenobiotics).Mercaptans, it has long been known, react with several heavy metals, including mercury. The formation of insoluble mercury complexes is characteristic of this class of compounds and is the source of the namemercaptan(mercurium captans, capturing mercury). Although not in current use, the dithiol 2,3‐dimercapto‐1‐propanol (BAL, dimercaprol, British anti‐Lewisite CAS Number [59-52-9]) was developed to protect against arsenical war gases (including Lewisite) and has been used as an antidote for exposure to arsenic, mercury, and other heavy metals. Interestingly, mercaptans such as the intracellular antioxidant glutathione activate the environmentally and occupationally important heavy metal Cr6+and also the economically important solvent methylene chloride to genotoxic products.