Studies of competitive

Dimension of constants k1 is (mole X 102 hr-Ikg-Iatm-2) and of adsorption coefficients K, is (atm-1)-b From the study of competitive system (Villa). 

From the study of competitive system (Vlllb). d From the rate data of the transformation of the given substance. 

Although the fate of Cr(IV) is uncertain, (cf. the alcohol oxidation), some characteristics of the intermediate chromium species have been obtained by Wiberg and Richardson from a study of competitions between benzaldehyde and each of several substituted benzaldehydes. The competition between the two aldehydes for Cr(VI) is measured simply by their separate reactivities that for the Cr(V) or Cr(IV) is obtained from estimation of residual aldehyde by a C-labelling technique. If Cr(V) is involved then p values for oxidation by Cr(VI) and Cr(V) are 0.77 and 0.45, respectively. An isotope effect of 4.1 for oxidation of benzaldehyde by Cr(V) was obtained likewise. 

This is the Schild equation, which was first stated and applied to the study of competitive antagonism by H. O. Schild in 1949. It is probably the most important single quantitative relationship in... 

The quantitative study of competitive antagonism by the methods just described has important uses ... 

There are at least two other studies of competitive reactions to form the products of solvolysis and elimination reactions that may provide insight into the relationships between carbocation structure and reactivity toward nucleophile addition and deprotonation. 

Gas-phase nucleophilic substitution reactions of Y-benzyl chlorides and X-phenoxide or X-thiophenoxide nucleophiles have been investigated by using the PM3 semiempirical MO method. The structure of the transition state was examined. The values of the gas-phase Hammett constants px and py are much greater than for the solution reactions, but a theoretical cross-interaction constant pxy (ca —0.60 for both phenoxides and thiophenoxides) agrees well with an experimental value of —0.62 for the thiophenoxide reactions in MeOH at 20 °C. Other work by the same group has involved theoretical studies of competitive gas-phase 5 n2 and E2 reactions of NCCH2CH2CI with HO and An ab initio method at the 6-31-l-G level was... 

Although nitrobenzene, nitrosobenzene and azobenzene are often observed in nitrobenzene hydrogenation, we are aware of no studies of competitive reactions. In this paper we report on the competitive hydrogenations and their mechanistic implications. 

Horne, D.S., Atkinson, P.J., Dickinson, E., Pinfield, V.J., Richardson, R.M. (1998). Neutron reflectivity study of competitive adsorption of p-lactoglobulin and non-ionic surfactant at the air-water interface. International Dairy Journal, 8, 73-77. 

Rather than discuss the estimation of the density of the diffusing species around other species, it is perhaps of more interest to estimate the rate coefficient for a reaction, and certainly rather less complex than estimating the density. One of the first such studies was by Reck and Prager [507]. They considered the diffusion of the fluorophor in solution amongst an array of stationary quenchers. The fluorophor was excited at a constant rate F s-1 and the deactivation occurred by natural decay (lifetime r) and by contact quenching. This model is very similar to that chosen by Felderhof and Deutch [25] in their study of competitive effects. 

In studies of competitive adsorption, the usually measured quantity is the overall composition of the adsorbed phase for a given composition of the bulk phase in equilibrium with it. It has been found that chemical shifts can provide a more detailed description. In a mixture of Xe and Kr in N 4 zeolite it was possible to observe the individual signals from XenKr mixed clusters as well as the Xen clusters under magic angle spinning (28). The absolute 129Xe chemical shifts of the XenKr mixed clusters and the increments between XenKr and the Xen+1 in various Xe-Kr mixtures in Na4 zeolite, are shown in Table I. 

Macoline Curarizing activity evaluated by studies of competitive binding of cholinergic receptor with labeled a-bungarotoxin 438... 

The activation energy computed by the Becke3LYP/6-31G method is in excellent agreement with the experimental value, whereas the activation energy values computed by other methods are too low. This is presumably because of the use of a UHF wavefunction and the overestimation of the stability of the diradical by the MP2 and MCSCF methods. It has been found in a number of earlier studies [64-66] that the < S2 > values calculated by DFT methods are usually very close to the expected value. This is also found in the case of the bond closure transition state, where the < S2 > value computed by the Becke 3LYP/6-31G and the UHF/6-31G methods are 0.17 and 1.05, respectively. This example provides another example which shows that appropriate DFT methods are useful for the study of competition between concerted and stepwise mechanisms. 

Reductive elimination is one of the most important fundamental bond-forming processes. Kinetic study of competitive... 

The first part of this paper is a critical review of model studies in cationic polymerization. In the second part we describe and discuss our investigations exploring the effect of a variety of alkylaluminum/alkyl halide initiating systems under a variety of conditions on the competitive reactions of the Keimedy-Gillham scheme (9). This scheme represents a comprehensive set of model reactions developed for the study of competitive reactions in cationic olefin polymerizatioa It involves the cationation of a nonpolymerizable (steric-hindrance) olefin under simulated polymerization conditions and the complete analysis of reaction products which in turn reflect initiation, propagation, termination and transfer. 

In 1970 Kennedy and Gillham (9) proposed a comprehensive scheme for the study of competitive reactions in cationk polymerization of isobutylene. Their scheme was based on reacting an initiator-coinitiator system with a nonpolymerizing olefin. In particular, they examined the t-BuQ/MejAl system with 2,4,4-trimethyl-l-paitene, the model compound for isobutylene, using methyl chloride at — 78°C. The overall reaction scheme is shown in Fig. 1. 

Our studies (19) indicated that proteins were readily adsorbed from aqueous solution onto hydrophobic polymer surfaces with Langmuir type adsorption and that the rate of adsorption toward a plateau surface concentration depends on the polymer nature. In the study of competitive adsorption from a protein mixture solution (20), fibrinogen and y-globulin adsorb onto FEP very rapidly compared with PEUU and SR. Therefore, the FEP surface in contact with blood has more acceptor sites for platelet adhesion than does the PEUU or SR surface. 

Calvo-Losada, S., Quirante, J. J. DFT study of competitive Wolff rearrangement and [1,2]-hydrogen shift of P-oxy-a-diazo carbonyl compounds. THEOCHEM1997, 398-399,435 43. 

Pelekani, C. and Snoeyink V.L. (2001). A kinetic and equihbrium study of competitive adsorption between atrazine and Congo Red dye on activated carbon the importance of pore size distribution. Carbon, 39(1), 25-37. 

The extensive literature of active nitrogen chemistry does not appear to record any study of competition between organic substrates. Such an investigation is capable of revealing whether the reactive species produced by attack on one substrate are capable of inducing attack on the second. Such information has some relevance to the role of attack... 

As stated previously, marketing must consciously decide the market in which the new product will compete. This will have involved in-market assessments and possibly laboratory studies of competitive product and national standards that govern sale, use and distribution. 

The procedures above are adequate for studies of competitive product formation but not for those of the overall reaction kinetics. In the latter case. 

When the primary rate information consists of a ratio of unimolecular rates (derived from the study of competitive reactions), all that is required is a ratio of product yields. This is most easily done by gas chromatography as in the Stem-Volmer analysis in which both products are stable molecules. The method is universal, easily calibrated, and therefore accurate. However, it contains no information about the product energy states. Also the reaction yield must be significant in order to be detectable. 

The discipline of DMPK has always been a drug development activity. In this realm, it still plays a pivotal role in describing the kinetic profile of the drug in both preclinical species and humans, where this information guides the selection of safe therapeutic doses for man for the first clinical studies, as well guiding the choice of dose frequency in patients. It is also important to describe accumulation, distribution and elimination profiles of the drug, its metabolic fate and the profiles of those key metabolites. The use of predictive tools to indicate metabolic fate is described in Chapter 11. The study of competition... 

In order to approach more closely to the blood system itself and to determine the influence of other proteins on fibrinogen adsorption, we undertook studies of competitive adsorption between fibrinogen and other plasma proteins. In these studies, etimes the adsorption of only fibrinogen (labelled with I) was followed sometimes that of both fibrinogen and a second protein (labelled with I) were followed. 

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