Sulfur atomic properties

There are three generally recognized classifications for sulfur vulcanization conventional, efficient (EV) cures, and semiefficient (semi-EV) cures. These differ primarily ki the type of sulfur cross-links that form, which ki turn significantly influences the vulcanizate properties (Eig. 8) (21). The term efficient refers to the number of sulfur atoms per cross-link an efficiency factor (E) has been proposed (20). 

The thiosulfate ion, 820 is a stmctural analogue of the sulfate ion where one oxygen atom is replaced by one sulfur atom. The two sulfur atoms of thiosulfate thus are not equivalent. Indeed, the unique chemistry of the thiosulfate ion is dominated by the sulfide-like sulfur atom which is responsible for both the reducing properties and complexing abiUties. The abiUty of thiosulfates to dissolve silver haUdes through complex formation is the basis for their commercial appHcation in photography (qv). 

Chlorosulfuric acid preparation and properties were described in 1854 (1), but the stmcture was debated for many years until it was shown in 1941 by magnetic susceptibiUty measurements that the chlorine was bonded direcdy to the sulfur atom (2). The chlorosulfuric acid stmcture (Cl—SO2—OH) is analogous to the stmcture of sulfuric acid, the chlorine replacing one of the hydroxyl groups (see SuLFURic ACID AND Sulfurtrioxide). This stmcture has been substantiated using Raman spectra (3,4). 

These reactions show sulfur in the role of an oxidizing agent. The properties of compounds such as ZnS suggest they contain the sulfide ion, S-2. The formation of this ion again can be expected on the basis of the fact that the neutral sulfur atom has two electrons less than enough to fill the valence orbitals. Acquisition of two electrons completely fills the low energy valence orbitals and solid ionic compounds can be formed. 

The stereogenic sulfur atom in sulfoxides is usually configurationally stable at room temperature thus, sulfoxides may be chiral based on this property alone1. In fact, there are many examples of optically active sulfoxides of both synthetic and natural origin. This chapter reviews the important methods for obtaining optically active sulfoxides, and discusses some reactions at sulfur which either leave the coordination number at three or increase it to four, generally with preservation of optical activity. It also describes briefly some recent studies on the conformational analysis and chiroptical properties of sulfoxides. 

Since it is clear that the presence of an unshared pair of electrons on the sulfur of the sulfoxide group leads to no special instability in the case of the known thiirene oxides (i.e., 18a, 28a,b and the first alkyl-substituted thiirene oxide 30 recently synthesized60), the reduced antiaromatic properties of the thiirene oxides relative to that of thiirenes have been manifested experimentally. As far as the possibility of electron-attracting conjugative stabilization involving the sulfur atom in thiirene oxides is concerned, the experimental evidence accumulated so far is not decisive. Thus, the chemical shift of the vinylic carbon of... 

Thiophene 1,1-dioxide (61) is too unstable to isolate and dimerizes with loss of S02 to give 3a, 7a-dihydrobenzothiophene 1,1-dioxide (172) in 34%113. However, alkyl-substituted thiophene 1,1-dioxides can serve as dienes in the Diels-Alder reaction, since the aromatic properties of the thiophene nucleus are lost completely and the n-electrons of the sulfur atom are used for forming the bond with oxygen. The sulfones 173-178 are found to react with two moles of maleic anhydride at elevated temperature to give bicyclic anhydrides114. Thus, at high reaction temperature, S02 is split off to give cyclohexadiene... 

The properties of some sulfide minerals can be discussed in a reasonably satisfactory way by assigning one or another of the structures of Table I to the sulfur atoms. For some minerals the ligancy of the sulfur atom is equal to its covalence, and for others it is greater, the bonds then having fractional bond numbers. It is often necessary to assign a hybrid structure to the sulfur atoms. I shall assume that the covalent bonds indicated in Table I always have the normal amount of covalent character, as given by the... 

Macrocycles containing nitrogen or sulfur atoms (e.g., 16 and 17) have similar properties, as do those containing more than one kind of hetero atom (e.g., 18, 19, or 20. ) Bicyclic molecules like 19 can surround the enclosed ion... 

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