Oxygen exchangers and

These observations illustrate that there are two transformations open to metallocarboxylic acid intermediates reversible loss of OH" accompanied by oxygen exchange, and metal-hydride formation with expulsion of C02. Our entry into this area of chemistry was in 1975 when extensive studies of oxygen lability in metal carbonyl cations were initiated (10). These... 

This is not exactly the order as the electronic conductivity of the oxides, indicating that electrocatalytic activity of mixed ionic and electronic conducting (MIEC) oxides depends on other properties such as the oxygen exchange and ionic conductivities. 

The different exchange processes described in Sections III-V can be combined to illustrate the reactivity of the different sites in these oxo cyano complexes as a function of pH and the possible interdependence thereof. The three processes that are compared are the inversion along the O-M-O axis (illustrated in Fig. 15 related to proton exchange), the oxygen exchange, and the cyanide exchange. 

The alkaline hydrolysis of esters has been studied in more detail, or at any rate more frequently, than any other chemical reaction, and results continue to appear in a steady stream. Since the gross mechanism is not in real doubt, this discussion will be limited mainly to the relationship between structure and reactivity in the reaction. The relationship can in most cases only be discussed for the overall reaction, which is, of course, of most immediate practical importance. Although it is of great interest to discover what effects structural changes may have on the separate steps of the reaction, it is only in the few cases where the oxygen exchange and hydrolysis reactions have been measured concurrently that this is possible. 

Concurrent carbonyl-oxygen exchange and hydrolysis in esters... 

Comparison of the activation parameters for carbonyl-oxygen exchange and for hydrolysis shows that, for the formamide, the rate of exchange is only slightly lower than that of hydrolysis, whereas in the case of acetamide and propionamide, the exchange occurs at a significantly lower rate. 

We have combined the results of three different types of measurement, enzyme-bound PPi, rates of H20-Pi oxygen exchange, and rates of PPi hydrolysis, to formulate the minimal scheme for PPase catalysis shown in equation (1), and to evaluate the rate constants contained within it (10). We note that all constants are apparent for pH 7.0... 

Hansen, L.K., Rathmann, 0., Olsen, A. Poulsen, K. (1997). Steam gasification of wheat straw, barley straw, willow and giganteus, Risp National Laboratory, Optics and Fluid Dynamics Department, Project No. ENS-1323/95-0010. Cerfontain, M,B Meijer, R., Kapteijn, F, Moutijn, J.A.(1987). Alkali-catalyzed carbon gasification in CO/CO2 mixtures An extended model for the oxygen exchange and gasification reaction, Journal of Catalysis, vol. 107, pp, 173-180. 

Bender s work does not prove the mechanism we have outlined. Conceivably, oxygen exchange—and hence the tetrahedral intermediate—simply represent a blind-alley down which ester molecules venture but which does not lead to hydrolysis. Such coincidence is unlikely, however, particularly in light of certain kinetic relationships between oxygen exchange and hydrolysis. 

Other related studies have dealt with the base hydrolysis of ds-[Co(en)2X(GlyO)] ions (X = Cl, Br) and oxygen exchange and glycinato ring opening in [Co(en)2(GlyO)]. ... 

Although the nitronium ion is the nitrating agent, there are known examples when nitration can occur in media in which the concentration of NOj is too small to be detected spectroscopically (Vol. I, pp. 25,48). This was pointed out by Bunton and Halevi [4] who succeeded in nitrating aromatic compounds with 40-60% aqueous nitric acid. Bunton and co-workers (5, 6) showed that the nitronium ion was an intermediate in both oxygen-exchange and aromatic nitration in the sense of reactions ... 

B.C.H. Steele, Isotopic oxygen exchange and optimisation of SOFC cathode materials, in F.W. Poulsen, J.J. Bentzen, T. Jacobsen, E. Skou and M.J.L. 0stergSrd (Eds.), High Temperature Electrochemical Behaviour of Fast Ion and Mixed Conductors. Riso National Laboratory, Denmark, 1993, pp. 423-430. 

Fig. 8. Relation between activation energy of oxygen exchange and the oxide formation heat, referred to 1 gm-atom of oxygen.

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