Oxygen exchange reaction rate

Isotopic exchange reaction rates and oxygen diffusion coefficients of Pt/M-CZ, S-CZ and R-CZ at 41 are listed in Table V (Dong et al., 2004a). The surface diffusion rate for R-CZ (Rg) is nearly 4 times larger than the bulk diffusion rate or the equilibrium isotopic exchange rate (R ), while it is... 

Table 22 Dependence of the Oxygen vs. Chlorine Exchange Reaction Rate upon the n Character of the P=0 Bond ...

Fig. 9. Rate coefficients for reactions of protonated ethyl acetate. The open circles represent data for hydrolysis. Closed circles are for the oxygen-exchange reaction of the carbonyl- 80 labelled...

Infrared spectroscopic studies (185-188) indicate that nitric oxide is adsorbed onto metal surfaces, not only as the familiar nitrosyl ligand but also as [N202] (hyponitrite) units. On metal oxide surfaces, chelating nitrite has also been detected, and such species are believed to be intermediates in oxygen-exchange reactions between N 0 and bulk oxide in NiO or Fo203. The rate of this process is measurable under conditions (e.g., room temperature) in which gas-phase dissociation is minimal. Spectroscopic studies also suggest that nitric oxide reacts... 

Molar flow rate of air feed and the sweep gas Oxygen permeation rate Reverse surface exchange reaction rate constant... 

Isotope shifts in C-n.m.r. spectra have been used to follow the kinetics of the oxygen exchange reactions at the anomeric centres of D-glucose, D-mannose, and D-fructose which are catalysed by acids and bases. The exchange rates were slow relative to mutarotation. Evidence from g.c. data on trimethylsityl derivatives of 2-deoxy-D-glucose and 2-deoxy-D-maltose suggested that the disaccharide in the crystalline state contains 83% of the a and 17% of the form. The enthalpy and entropy of interaction of cations with hexoses and pentoses is referred to in Chapter 17. 

The operation of the nitronium ion in these media was later proved conclusively. "- The rates of nitration of 2-phenylethanesulphonate anion ([Aromatic] < c. 0-5 mol l i), toluene-(U-sulphonate anion, p-nitrophenol, A(-methyl-2,4-dinitroaniline and A(-methyl-iV,2,4-trinitro-aniline in aqueous solutions of nitric acid depend on the first power of the concentration of the aromatic. The dependence on acidity of the rate of 0-exchange between nitric acid and water was measured, " and formal first-order rate constants for oxygen exchange were defined by dividing the rates of exchange by the concentration of water. Comparison of these constants with the corresponding results for the reactions of the aromatic compounds yielded the scale of relative reactivities sho-wn in table 2.1. 

The hydration reaction has been extensively studied because it is the mechanistic prototype for many reactions at carbonyl centers that involve more complex molecules. For acetaldehyde, the half-life of the exchange reaction is on the order of one minute under neutral conditions but is considerably faster in acidic or basic media. The second-order rate constant for acid-catalyzed hydration of acetaldehyde is on the order of 500 M s . Acid catalysis involves either protonation or hydrogen bonding at the carbonyl oxygen. 

M s , in agreement with independent measurements of the rate of hydration. Thus, it appears that the oxygen exchange rate can be completely accounted for by the hydration reaction. 

The radioisotope Cr was used to tag the species and the separation of Cr from CrX " was achieved using an ion-exchange method, after oxidation of the Cr to Cr with Fe(III) or oxygen. The reactions were carried out in the absence of oxygen in perchlorate media. For the systems involving chloride, fluoride, and azide . King et al. have found a rate law... 

---