Nitrogen kinetic constant

Table 5. Experimental kinetic constants for nitriding of titanium, niobium and molybdenum immersed in a low pressure nitrogen discharge at floating potential (according to Ref.189b- A is the preexponential factor,...

Table 5. Steady-state concentrations of nitric oxide and kinetic constants for a stoichiometric nitrogen-oxygen mixture at 50 torr in the presence of catalysts in the interelectrode space...

Table 6. Activities of catalysts placed in the interelectrode space and kinetic constants for difTerent compositions of nitrogen-oxygen mixtures ... 

The major disadvantage of the present design of the wall-less reactor is the diffusion of the injected center stream into the surrounding nitrogen. Accordingly, if more than one reactant is involved or if the reaction is higher order, the reproducibility is equally good, but calculations of the rate parameters are made much more complicated. In this paper calculations of the kinetic constants are made only from the nonoxidative rate... 

Kinetic and equilibrium data were obtained using a batch column device described elsewhere [39,40]. At 25 C, the oxygen and nitrogen monolayer capacity is 1.8 mole/kg CMS, and the adsorption and desorption kinetic constants are, respectively, 76.84 cm3/(mole s) and 0.0176 1/s for oxygen, and 3.11 cm V(mole s) and 0.000585 1/s for nitrogen. 

Steady-State Runs. Four levels of residence times were employed 0.273, 0.352, 0.54 and 1.33 seconds. Each set of runs was conducted over a wide range of ratio of reactants in the feed stream, keeping the nitrogen composition constant throughout at 60%, and the water bath temperature at 70°C. The objective of these runs was to establish experimentally the conditions for optimum steady-state yield, and to determine the kinetics... 

The steric and electronic effects of substituents on the electrophilic attack at the nitrogen atom have been discussed in the general chapter on reactivity (Section 4.02.1.3). All the conclusions are valid for pyrazoles and indazoles. The effect on equilibrium constants will be discussed in detail in the sections dealing with values (Sections 4.04.2.1.3(iv) and (v)) and the kinetic effects on the rates of quaternization in the corresponding section (4.04.2.1.3(vii)). 

Such modifications can be produced either in the kinetic aspects (proton transfer) or in the equilibrium constant. Both effects are mediated by intramolecular hydrogen bonds. For instance, Navarro et al. (93MI69) showed that the rate of proton transfer between the two nitrogen atoms of pyrazole (annular tautomerism) is considerably reduced in macrocycles containing oxygen or nitrogen atoms in the macroring. 

Asano and co-workers have reported die kinetic effects of pressure, solvent, and substituent on geometric isomerization about die carbon-nitrogen double bond for pyrazol-3-one azomethines 406 (R = H), 406 (R = NO2) and 407, (Scheme 93). The results demonstrate the versatility of die inversion mechanism. The rotation mechanism has been invalidated. First-wder rate constants and activating volumes for diermal E-Z isomerization for 406 (R = H) and 406 (R = NO2) are given at 25°C in benzene and methanol (89JOC379). 

The fundamental understanding of the diazonio group in arenediazonium salts, and of its reactivity, electronic structure, and influence on the reactivity of other substituents attached to the arenediazonium system depends mainly on the application of quantitative structure-reactivity relationships to kinetic and equilibrium measurements. These were made with a series of 3- and 4-substituted benzenediazonium salts on the basis of the Hammett equation (Scheme 7-1). We need to discuss the mechanism of addition of a nucleophile to the P-nitrogen atom of an arenediazonium ion, and to answer the question, raised several times in Chapters 5 and 6, why the ratio of (Z)- to ( -additions is so different — from almost 100 1 to 1 100 — depending on the type of nucleophile involved and on the reaction conditions. However, before we do that in Section 7.4, it is necessary to give a short general review of the Hammett equation and to discuss the substituent constants of the diazonio group. 

The mechanism of decarboxylation of acids containing an amino substituent is further complicated by the possibility of protonation of the substituent and the fact that the species NH2ArCOOH is kinetically equivalent to the zwitterion NHj ArCOO. Both of these species, as well as the anion NH2 ArCOO" and even NH3 ArCOOH must be considered. Willi and Stocker644 investigated by the spectroscopic method the kinetics of the acid-catalysed decarboxylation of 4-aminosalicyclic acid in dilute hydrochloric acid, (ionic strength 0.1, addition of potassium chloride) and also in acetate buffers at 20 °C. The ionisation constants K0 = [HA][H+][H2A+] 1 (for protonation of nitrogen) and Kx = [A"][H+] [HA]-1, were determined at /i = 0.1 and 20 °C. The kinetics followed equation (262)... 

Having estimated the sticking coefficient of nitrogen on the Fe(lll) surface above, we now consider the desorption of nitrogen, for which the kinetic parameters are readily derived from a TPD experiment. Combining adsorption and desorption enables us to calculate the equilibrium constant of dissociative nitrogen adsorption from... 

Numerous quantum mechanic calculations have been carried out to better understand the bonding of nitrogen oxide on transition metal surfaces. For instance, the group of Sautet et al have reported a comparative density-functional theory (DFT) study of the chemisorption and dissociation of NO molecules on the close-packed (111), the more open (100), and the stepped (511) surfaces of palladium and rhodium to estimate both energetics and kinetics of the reaction pathways [75], The structure sensitivity of the adsorption was found to correlate well with catalytic activity, as estimated from the calculated dissociation rate constants at 300 K. The latter were found to agree with numerous experimental observations, with (111) facets rather inactive towards NO dissociation and stepped surfaces far more active, and to follow the sequence Rh(100) > terraces in Rh(511) > steps in Rh(511) > steps in Pd(511) > Rh(lll) > Pd(100) > terraces in Pd (511) > Pd (111). The effect of the steps on activity was found to be clearly favorable on the Pd(511) surface but unfavorable on the Rh(511) surface, perhaps explaining the difference in activity between the two metals. The influence of... 

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