Oxygen-18 exchange studies

The significant reactivity difference for cyanide exchange on the Tc(V) and Re(V) of >4000 is in general agreement with that found in previous complex-formation and oxygen-exchange studies (1, 2, 76,... 

Fundamental insight into the oxidation catalysis over oxides can be provided by isotopic oxygen exchange studies. Predominantly, studies have involved the exchange of and 0, although the use of the rarer isotope has advan-... 

Lao.6Sro.4Coo.2Feo.803 g (LSCF) was processed in the same manner as for membrane preparation in order to generate an identical microstructure. The powder was dry pressed into a sintered pellet and was crushed and sieved for TGA and oxygen exchange studies. 

The chemical properties of oxide surfaces have been studied by several methods, including oxygen exchange. This method has been used to investigate the mechanisms of heterogeneous reactions for which oxides are active catalysts [36]. The dimerization step does not necessarily precede desorption and Malinin and Tolmachev [634], in one of the few reviews of decomposition kinetics of solid metal oxides, use this criterion to distinguish two alternative reaction mechanisms, examples being... 

The reported in situ NMR of combustion [2] served largely as proof of concept work. It was demonstrated that despite the presence of paramagnetic oxygen and radicals, the xenon relaxation times are sufficiently long for gas exchange studies. 

Kinetic studies on racemization, oxygen exchange reaction using H2lsO, and theoretical studies clarified the mechanism for racemization of optically active chalcogenic acids.34,37 The mechanism of racemization of tellurinic acids is different from that of the corresponding seleninic acids. In fact, the mechanism for racemization of optically active tellurinic acids was found to involve an... 

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... 

The oxygen exchange on the different oxo complexes for the W(IV), Mo(IV), Tc(V), Re(V), and Os(VI) metal centers were studied as described below in more detail. A summary of the rate constants thus obtained are given in Table V. 

The effect of temperature and [H+] on the oxygen exchange was studied for the W(IV) system by simple pH manipulation as was the case for the Re(V) mentioned above. However, here the pH had to be varied around high values (12-14) to attain the slow isotopic exchange conditions. The kinetic results were treated similarly to those of the Re(V) and are listed, together with the activation parameters, in Table V. 

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