Sulfur Engel

Rhombohedral sulfur Aten sulfur Engel sulfur e-Sulfur p-Sulfur Rhombohedral (p) sulfur Crystalline cyclo-Se Space group R3... 

We now consider other homocyclic polymorphs of sulfur containing 6 - 20 S atoms per ring. A rhombohedral form, t-sulfur, was first prepared by M. R. Engel in 1891 by the reaction of concentrated HCl on a saturated solution of thiosulfate HS2O3 at 0°. It was shown to be... 

Sulfur can form rings and chains of various shapes and sizes. In addition to the crown-shaped cyclo-Sg, nine other types of rings can be prepared the first of these, cyclohexasulfur, also called Engel s or Aten s sulfur, or rhombohedral sulfur, Sp, was first described by Engel in 1891 (28). The other eight types of rings were all discovered during the last 10 years by Schmidt and his co-workers (87,88) notably Wilhelm (125). 

Fig. 1. Electrode potential of Feg 94O as a function of dissolution rate (expressed in current density) in sulfuric acid and hydrochloric acid [ Engell, Z. physik. Chem. N. F., 7, 158 (1956)]...

Engel, K. H., Tressl, R. (1991). Identification of new sulfur-containing volatiles in yellow passion fruits (Passiflora edulis f. flavicarpa). J. Agric. Food Chem., 39, 2249-2252. 

Figure 9. Schematic diagram showing sulfur photochemistry in an anoxic, primitive atmosphere. The numbers at the base of the diagram indicate the oxidation state of the sulfur. Sulfur is emitted to the atmosphere from volcanoes as either SO2 or H2S. It is removed by rainout of soluble sulfur gases fS02, H2S, HS, HSO, and H2SO4) and by formation of sulfate and elemental sulfur particles (Engel and Macko. 199S).

Neda, C. Melnicky, A. Vollbrecht, A. Fischer, P.G. Jones, A. Martens-von Salzen R. Schmutzler, U. Niemeyer B. Kutscher, and J. Engel, Phosphorus, Sulfur and Silicon, 1996,109-110, 629. 

Sulfur compounds in the thiol family (or mercap-tans) are generally held responsible for olfactory defects (Section 8.2.2). However, their major contribution to the aromas of certain fruits and aromatic plants has been clearly estabhshed. Thus, specific thiols are involved in the characteristic aromas of fruits such as blackcurrant (Rigaud et al., 1986), grapefruit (Demole et al., 1982), passion fruit (Engel and Tressel, 1991) and guava (Idstein and Schreier, 1985 Bassols and Demole, 1994). Two mercaptans, ethyl-3-mercaptopropion-ate and ethyl-2-mercaptopropionate, have been identifled as components in the aroma of Vitis labrusca grapes (variety Concord) (Kolor, 1983 Winter et al, 1990). 

Pti-x ZXjc supported on carbon or alumina, Kt/Kb is proportional to x, suggesting electron transfer from platinum to zirconium, as predicted by the Engel-Brewer theory, and (2) chemisorption of sulfur on platinum has been shown to decrease electron density of the surface, while carbon has the opposite effect. The ratio Kt/Kb was very large for ruthenium, about 10 for rhodium and about unity for palladium, which may help to explain their different activities in these and other reactions. An extensive kinetic study of the hydrogenation of mixtures of benzene and toluene on NiA zeolite has however revealed a situation of some complexity, and it is not certain that the original simple concept is totally valid. 

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