IT'S ELEMENTAL!
conductivity similar to iron. This pioneering work eventually led to the fundamental discovery of organic conducting polymers, and in turn to the award of the Nobel Prize in Chemistry to MacDiarmid, Heeger, and AMOS B. SMITH I I I , UNIVERSITY OF PENNSYLVANIA Hideki Shirakawa in 2000. O MANY PEOPLE, THE ELEMENT respectively as diatomic molecules or take Organosulfur compounds, equally widesulfur quickly brings to mind on polymorphic networks, the four isotopes spread in nature, are essential for all living unpleasant memories of rotten ofsulfurpS(95.1%),33S(0.74%),34S(4.2%), organisms. Particularly important are the eggs and unwelcome encoun- and36S (0.016%)} combine to form aunique- amino acids cysteine and methionine. Cysters with skunks. While true ly large number of allotropic forms (com- teine possesses the unique thiol (-SH) that many sulfur-containing compounds, pare SH9 where n = 1-12,18, and infinity). Of functionality, which plays a critical role in such as mercaptans, thioethers, and disul- these, only eight have been characterized the folding and three-dimensional strucfides, possess remarkably foul odors, ele- crystallographically. The most common tures of proteins through formation of mental sulfur (S) in pure form is com- form, stable at room temperature and at- cross-linking disulfide bonds. Methionine, pletely odorless, tasteless, and by and large mospheric pressure, is orthorhombic sulfur in the form of 5-adenosylmethione, is nanontoxic. (Sg). Here, eight sulfur atoms bond cova- ture's methylating agent. Other important lendy in crownlike rings. This al- sulfur-containing biomolecules include kerReferred to in Genesis as brimlotrope, also known as rhombic atin, biotin, thiamine, coenzyme A, glustone, meaning "a stone that sulfur, Muthmann's sulfur, and a- tathione, and lipoic acid. burns," elemental sulfur, which S, was among the first substances does readily burn in air, has been In synthetic chemistry, sulfur plays a to be examined crystallographi- central role, especially in its oxidized forms. known since ancient times. The cally by William Bragg in 1914. word derives fromsutvere mdsulDimethylsulfoxide (DMSO), a commonphur (Sanskrit and Latin, respecThe chemistry of sulfur is ly used organic solvent with invaluable soltively). Major sulfur deposits are equally complex; it combines ubility properties, is the key reagent in the found in the salt domes ubiquiwith many elements to yield a widely used Swern oxidation of alcohols. THIS ELEMENT tous to the GulfCoast ofthe U.S.; BROUGHT bewildering array ofboth organ- Enantiomerically pure sulfoxides, sulfoxTO YOU BY sulfur is the 16th most abundant ic and inorganic compounds. imines, and derivatives make superb chiral ATOFINA element in nature. Recovery is by Common inorganic compounds melting with superheated water, a include sulfur hydrides, carbon SULFUR AT A GLANCE commercial process developed by Herman disulfide (CS2), sulfur selenides, and sulfur Frasch in the 1890s and still in use today halides (SX^. Oxides of sulfur are particuName: From the Sanskrit sutvere and Sulfur is also a major by-product of and larly important, possessing both beneficial the Latin sulphur. can be extracted from coal, ores, and min- and deleterious properties. Sulfur dioxide Atomic mass: 32.07. erals such as gypsum, cinnabar, barite, and (SO2), for example,findsbeneficial use in History: Known to ancient civilizations. pyrite (fool's gold). From an economic per- preserving fruits and vegetables and in the Occurrence: Found near hot springs, spective, most of the world's sulfur produc- brewing and wine-making industry as both geysers, and volcanoes. tion is used to make sulfuric acid (F^SO^, an antioxidant and an antibiotic. Sulfur Appearance: Pate yellow, brittle solid. approximately 40 million tons every year dioxide and its close relative, sulfur trioxBehavior: Elemental sulfur is relatively just in the U.S. Fertilizers and lead-storage ide (SO3), represent serious hazards, arising nontoxic, but its simple derivatives can automobile batteries consume a large por- in the environment principally by burning be harmful. S02 is indicated in atmostion of this supply, with smaller amounts of sulfur-rich fuels such as coal and oil or by pheric air pollution. used as insecticides, as dyeing agents, in the smelting ores. Released into the atmosphere Uses: Used in fireworks, gunpowder, manufacture of gunpowder, and to vulcan- and combined with water, these pollutants fungicides, and preservatives. form sulfuric acid and in turn acid ize natural and synthetic rubbers to impart rain, a cause of huge economic auxiliaries and reagents for many asymdesirable mechanical properties. damage. Since sulfur is positioned directmetric reactions (for example, Davis oxily under oxygen in the periodic In combination with dation andJohnson resolution), while sultable, one might suspect relfones and dithianes are utilized extensively v , nitrogen, sulfur forms atively simple besulfur nitride (S4N4), to form cr- and n-carbon-carbon bonds (for havior at the precursor to the sulfur- example, Julia olefination and Corey-Seeatomic level. This nitrogen inorganic bach umpolung chemistry). In our and othis certainly not the polymer (SN)X, which ers' laboratories, dithianes have found excase! Indeedjerry was shown in 1975 by my tensive use in mono- and multicomponent fragment unions for the construction of Donohue, in his auv complex natural products possessing imthoritative treatise, CLUMPED Sulfur portant bioregulatory properties. 'The Structures of the Ele produces a monoclinic shape ments," argues, "Of all of the elements, sul- when crystallized out of solution. fur presents the most confusion and comAmos B. Smith III is the Rhodes-Thompson plexity in this respect." Unlike sulfur's near colleagues at the University of Pennsylva- Professor of Chemistry and a member of the neighbors, such as N, O, CI, and Br, or P, As, nia, Alan G. MacDiarmid andAlanJ. Heeger, Monell Chemical Senses Center at the UniverSe, andTe, which in elemental form exist to be a metal at room temperature with a sity of Pennsylvania.
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C&EN / SEPTEMBER 8, 2003
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