Sulfates structural chemistry

In addition to the handbooks, a number of reviews and theses of more limited scope have recently appeared. The overviews of Niinisto (1983, 1984b) discuss the structural and thermochemical aspects of rare earth sulfates, while the thesis by Lindgren (1977e) provides a summary of the structural chemistry of Ce and Ce sulfates. The review by Voronkov et al. (1982) is also specialized in that it... 

The condensation chemistry allows films of various compositions, as the addition of sulfate renders the materials amorphous over a range of concentrations as implied by the acronym HafSOx, where x typically assumes values of 0.3-1 (refer to Fig. 4.3, where the top reaction sequence represents x = 0.5.) The amorphous character and structural integrity are retained until the material decomposes with stoichiometric loss of S03(g) at approximately 700 °C. The smoothness and uniformity of deposited films are illustrated by the Scanning electron microscope (SEM) images in Fig. 4.4. Rapid kinetics, absence of organics, and facile condensation all play important roles in the deposition of these dense HafSOx films. 

Another type of hypervalency is encountered in textbook descriptions of the oxyanions of common laboratory acids. Generations of chemistry students have been taught that the correct representations of these species are in terms of resonance-delocalized hypervalent Lewis-structure diagrams, such as sulfate (S042-),... 

J. Hanna, Fundamentals of Chemistry, revised and enlarged edition (Boston, Houghton Mifflin, 1929), showing how the original Lewis structure for the sulfate anion was first presented in general chemistry textbooks. As the authors note (p. 132), Dr. G. N. Lewis, of the University of California, has advanced an explanation that is now generally accepted (1928-1929). ... 

The oxo-transfer chemistry of molybdenum in sulfite oxidase is probably the best characterized, in terms of synthetic models, structural and mechanistic data, of all the elements we have described up till now. The reaction cycle (Figure 17.5) involves binding of sulfite to the oxidized MoVI, two-electron reduction of the Mo centre and release of sulfate. The Movl centre is restored by successive one-electron transfers from a cytochrome (bs in mammals). The primary oxo-transfer reaction ... 

Considering the impressive amount of literature on sulfated zirconia and solid superacids,125 134-139 it will be difficult to impose a definition a posteriori. On the other hand, due to the large difference in acidity and in structure between various liquid superacids, there is no unique chemistry of hydrocarbons in liquid superacids. For this reason it is not possible to suggest a unequivocal definition of solid superacidity at the present stage. Nevertheless, it seems clear from all the data presently available that at high temperatures the chemical reactivity of the proton bound to the surface shows a close resemblance to the one observed at low temperature in liquid superacidic media as will be seen in Chapter 5. 

Other intermediate-duration oral studies in rats evaluated effects of aluminum on brain chemistry as well as neurobehavioral performance. Rats that consumed 51 mg Al/kg/day as aluminum chloride in drinking water for 180 days had alterations in behavior (reduced spontaneous locomotor activity, impaired learning, extinction and relearning of an active avoidance task, impaired maze relearning ability) and brain chemistry (increased lipid peroxidation, decreased activity of Na+-, K+-, and Mg2+-ATPases) (Lai et al. 1993). Ingestion of 490 mg Al/kg/day as aluminum sulfate in drinking water for 4-12 weeks caused reduced retention of a learned passive avoidance task and changes in brain chemistry (e.g., increased cyclic adenosine monophosphate levels, decreased concentrations of MAP-2 and other structural... 

---