Kinetic data nitrogen

Nevertheless, the puzzling fact to be explained is that the harder ring nitrogen prefers the softer electrophilic center and that this preference is more pronounced than the one observed for the amino nitrogen. Much remains to be done to explain ambident heterocyclic reactivity it was shown recently by comparison between Photoelectrons Spectroscopy and kinetic data that not only the frontier densities but also the relative symmetries of nucleophilic occupied orbitals and electrophilic unoccupied orbitals must be taken into consideration (308). 

Curiously enough, bulky substituents on nitrogen increase this reactivity towards methyl iodide (119). This has been related to a steric decompression of the thiocarbonyl group in the transition state. Furthermore, knowledge of the ratio of conformers in the starting 4-alkyl-3-i-Pr-A-4-thiazoline-2-thiones and in the resulting 4-alkyl-3-i-Pr-2-methylthiothi-azolium iodides combined with a Winstein-Holness treatment of the kinetic data indicates that in the transition state, the thiocarbonyl bond is approximately 65% along the reaction coordinate from the initial state... 

Kinetic data on acetate displacement from C-3 using a number of sulfur and nitrogen nucleophiles in aqueous solution at near neutral pH demonstrate that the reaction proceeds by an 5 1 mechanism (B-72MI51004). The intermediate in this reaction is depicted as a dipolar allylic carbonium ion (9) with significant charge delocalization. Of particular significance in this regard is the observation that the free carboxylate at C-4 is required since... 

This sequence is presented by structural formulas in Scheme I, where the designations p + 2o + m, etc., refer to the number and position para, ortho, meta) of the activating ring-nitrogens relative to the leaving group (Le). The azinyls marked with a superscript a are in predicted locations. There is kinetic data available on those marked with a superscript b and synthetic organic comparisons on those marked with superscript c. ... 

The effect of hydrogen bonding to nuclear substituents in transition states is reviewed in Sections I,D, 2,b, and II, E. Relative reactivity at different ring-positions is postulated to be alterable by hydrogen bonding of an azine-nitrogen to the solvent or to the reagent (Section II, B, 3 and III,B). However, there appears to be no kinetic data relevant to this postulate. 

No kinetic data or semi-quantitative comparisons among themselves or with other diazines are available. The most reactive derivative is expected to be the 4-substituted-l,6-naphthyridine (425), with 2-substituted-1,6- and l-substituted-2,7-naphthyridines (426) somewhat less reactive, all three positions being activated by two ring-nitrogens by resonance. Other positions also activated in this way... 

Various other heteroatom-centered radicals have been generated as initiating species. These include silicon-, sulfur-, selenium- (see 3.4.3.1). nitrogen- and phosphorus-centered species (see 3.4.3.2). Kinetic data for reactions of these radicals with monomers is summarized in Table 3.10. 

The second test for the mechanism shown in Scheme 8-8 is to apply equation (c) to (8-10) with kinetic data for dediazoniations with varying concentrations [N2] of molecular nitrogen. As the solubility of N2 is quite low in most solvents, kinetic measurements must be made under N2 pressure. The dediazoniation reaction has a... 

In all of the above cases involving decompositions of vinyl diazonium ions, the observed products are consistent with a vinyl cation formulation, but extensive mechanistic studies of these reactions have not been reported. It is difficult, for instance, to establish to what extent reaction proceeds through the diazonium ion via a backside nucleophilic attack and concerted loss of nitrogen rather than through the free vinyl cation. In the absence of kinetic data, it is also difficult to rule out competing or alternative mechanisms not involving vinyl cations. 

In this paper we summarize some of the results of our measurements of rates of dry oxidation. Results of chemical analyses of residues produced by heating in flowing nitrogen atmosphere (distillation) are also reported and combined with our kinetic data to obtain values of kinetic parameters. Preliminary results of measurements of rates of wet oxidation are presented. 

The difference in mole fractions is most significant in the case of S02 where this difference is 15% of the bulk phase level. This result indicates that external mass transfer limitations are indeed significant, and that this difference should be taken into account in the analysis of kinetic data from this system. Note that there is a difference in nitrogen concentration between the bulk fluid and the external surface because there is a change in the number of moles on reaction, and there is a net molar flux toward... 

Kinetic data on cyclohexene hydrogenation catalyzed by RhClL species (n = 1, 2, or 3 L = p-dimethylaminophenyl phosphines) were interpreted in terms of active dimer catalysts (cf. 1), possibly involving coordination through nitrogen as well as phosphorus (82). 

The kinetic data for reactions of nitrogen-centered radicals with silicon hydrides is limited to rate constants for piperidinyl radical 18 (Table IV) by using ESR spectroscopy.61 The two remarkable features of the data are... 

The limited kinetic data for reactions of tin hydride with nitrogen-centered radicals apparently demonstrates the combined effects of the enthalpies of the reactions and polarization in the transition states for H-atom transfer. The aminyl and iminyl radicals are electron-rich, and the N-H bonds formed are relatively weak these radicals react relatively slowly with tin hydride. On the other hand, the electrophilic amidyl and aminium cation radicals form strong N-H bonds and react rapidly with the tin hydride reagents. 

Table 2 Representative kinetic data for the nitrogen atom transfer reactions by osmium(VI) nitrido...

A simple numerical soln is developed. General theory developed is check by expts with expln flame of 03 andO. for which complete and reliable kinetic data are available. General theory is applied to mixts of Methane and Nitrogen air, helium air, and argon air. 

In order to demonstrate the effect, it was felt that cleaner kinetic data was needed. This was secured by modification of the participants in the cycloaddition. A tertiary butyl group was introduced onto the amino nitrogen of each substrate (Fig. 7, R = t-Bu). This renders the reaction noncatalytic in the strict sense. Because the tert-hutyl substituents are too large to pass through the cavity of cucurbituril, the resulting product of cycloaddition is a stable rotaxane, i.e. the triazole cannot dissociate. However, this is desirable in that the chemically meaningful presteady-state phase becomes delineated in a way that could only be incompletely realized in the previous kinetics. As a bonus the undesirable substrate inhibition by propargylammonium ion, which also obscured earlier kinetic measurements, could be avoided as well. 

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