Oxygen interaction with the

Gland JL, Sexton BA, Fisher GB. 1980. Oxygen interactions with the Pt(lll) surface. Surf Sci 95 587-602. 

First, solvent molecules, referred to as S in the catalyst precursor, are displaced by the olefinic substrate to form a chelated Rh complex in which the olefinic bond and the amide carbonyl oxygen interact with the Rh(I) center (rate constant k ). Hydrogen then oxidatively adds to the metal, forming the Rh(III) dihydride intermediate (rate constant kj). This is the rate-limiting step under normal conditions. One hydride on the metal is then transferred to the coordinated olefinic bond to form a five-membered chelated alkyl-Rh(III) intermediate (rate constant k3). Finally, reductive elimination of the product from the complex (rate constant k4) completes the catalytic cycle. 

For an example of combining insights from DFT calculations and experiments to understand oxygen interactions with the technologically important Ti02 surface see M. A. Henderson, W. S. Epling, C. L. Perkins, C. H. F. Peden, and... 

In addition, the infrared examination of the mechanism of propane and oxygen interaction with the sample (Fig. 6) indicates the different mechanism of interaction of the intermediate propylene as compared to other supported vanadium catalysts such as V-Ti02 (10). In particular, the formation of a 7t-bonded complex stabilized by a nearlying silanol with weak basic character due to the inductive effect of vicinal vanadium is shown. This indicates the relative inertness of the V sites in the silicalite towards 0-insertion or allylic H-abstraction on the adsorbed propylene. It is evident that the reduced reactivity of V sites in these reactions limits the consecutive reactions of intermediate propylene, thus enhancing the selectivity in the formation of this product. 

The increase of the heat of adsorption of oxygen when the adsorption temperature increases was explained in Section III, A by the enhancement of the outward mobility of surface ions and consequently by a surface modification. The present results show moreover that a permanent modification of the surface occurs at high temperatures (200-250°) when oxygen interacts with the solid and that removal of this oxygen does not restore the original surface structure. These modifications occur more rapidly at 250° than at 200°, probably because of the enhanced surface mobility at the higher temperature, and three catalytic runs and regeneration treatments produce at 250° the same modifications of surface structure of the catalyst [NiO(250°)] that four cycles of... 

The next stage of oxygen interaction with the Pt SE of the YSZ-based sensor is the electrochemical reaction of oxygen ionization at the TPB. We assume that the oxygen atom accepts two electrons from the Pt SE at the TPB and as ion transfers... 

A host-guest complex, 41, of silver with a bis-ferrocene cryptand has been thoroughly investigated, revealing strong evidence of an interaction between Ag+ and the ferrocene unit, in addition to silver nitrogen (and some silver oxygen) interactions with the macrocycles [85]. 

The interaction between the two elements appeared to be influenced mainly by the temperature and only slightly by the reaction environment during further treatments. However, the thermal treatment of the catalyst at 350 °C, in air or toluene, was accompanied by a partial reduction of Fe that has been compensated by a partial oxidation of Eu. Both toluene and gaseous oxygen interacting with the surface as 02 > O-f, or 0 chemisorbed species agreed with a Volken-stein mechanism (Scheme 18.1). 

The reaction of singlet oxygen with the enolic tautomers of l-(2, 4 6 -trialkylphenyl)-2-methyl 1,3-diketones is proposed to proceed via one of two transition states, one in which the incoming singlet oxygen interacts with the allylic hydrogen atoms (less polar), and the other in which it interacts with the enol hydroxyl group (more polar). The former case leads to the 3-hydroxy peroxide, which is converted into the enedione and the epoxy ketone the latter is converted directly into the hydroperoxy ketone. 

FIGURE 4.20. WF changes of undoped NiO during sorption of oxygen in the temperature range 20 to 400°C and related mechanism of oxygen interaction with the NiO lattice. (From Nowotny, J., in Science of Ceramic Interfaces, Nowotny, J., Ed., Elsevier, Amsterdam, 1991, 79-204. With permission.)... 

However, this potential will not be observed because neither oxidant (glucose) nor reductant (oxygen) interacts with the anode and cathode directly. Rather, this interaction is mediated by the osmium compounds. In practice, the open-circuit potential observed will be shghtly higher than the difference in the mediator redox potentials (Equation 9.5) ... 

The substrate-binding site contains Arg-35, Lys-84, Tyr-85, and Arg-87 residues. They assist in positioning the 3 -P and 5 -P of pdTp in the nuclease complex. The positive side chains of the two Arg residues are H-bonded to the oxygen atoms of the 5 -phosphate, activating it to nucleophilic attack. The 3 -phosphate oxygens interact with the side chain of Lys-84 and the phenolic OH of Tyr-85. 

In almost the same period, Uraguchi and Terada reported the direct Mannich reaction of N-Boc-protected imines with acetyl acetone (Scheme 11.2) [5]. In their direct Mannich reaction, phosphoric acid also worked as a dual functional catalyst the Br0nsted acidic moiety of phosphoric acid catalyst Ic activated aldimines 5, and the Lewis basic site (phosphoryl oxygen) interacted with the O-H proton of the enol form of 6. As a result, the reaction proceeded under a chiral environment created by phosphoric acid 1, acetyl acetone, and aldimine through hydrogenbonding interactions to furnish optically active products 7. 

The mode and orientations of interaction of urea molecules with these surfaces are shown in Figure 8.1. The urea moiety prefers to interact with both the potassium and chloride ions in 100 and 110 surfaces. The carbonyl oxygen of urea interacts with the potassium ion, whereas the hydrogen of amine functionality interacts with the chloride ion. In the case of the 111 surface of KCl, the carbonyl oxygen interacts with the potassium ion. 

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