Ivanov model

Fig. 6.8. The dependence of rj2 on x) by the Ivanov model (I) and friction model (F) in comparison with predictions of the extended. /-diffusion (ED) and Langevin (L) models for linear molecules. The line (H) corresponds to the Hubbard inverse proportionality between xgj and xj at very high densities. Experimental data from [81] are in rectangles around line G with the length of their vertical and horizontal sides being equal, correspondingly, to the experimental errors in x el and rj measurements. Experimental data from [270] (J) are shown both in original position and shifted down by a factor of four (broken line).

Valiev-Ivanov model 219, 275 vibrational broadening 123 vibrational dephasing 111, 113-15, 123 vibrational relaxation, and angular momentum relaxation 92 vibrational transition, adiabatic dephasing 92... 

In the field of the glass transition, the molecular orientation/position is often considered as a stochastic process and the dynamics is described in the framework of the Ivanov model, i.e., the molecular orientation/position is assumed to be constant... 

A completely different dipolar cycloaddition model has been proposed39 in order to rationalize the stereochemical outcome of the addition of doubly deprotonated carboxylic acids to aldehydes, which is known as the Ivanov reaction. In the irreversible reaction of phenylacetic acid with 2,2-dimethylpropanal, metal chelation is completely unfavorable. Thus simple diastereoselectivity in favor of u f/-adducts is extremely low when chelating cations, e.g., Zn2 + or Mg- +, are used. Amazingly, the most naked dianions provide the highest anti/syn ratios as indicated by the results obtained with the potassium salt in the presence of a crown ether. 

The kinetic model of Ivanov and Balzhinimaev (1987) and Balzhinimaev et al. (1989) assumes that the steps in the mechanism of Table III are elementary and that the active and inactive forms of the complexes are in equilibrium. Table IV presents the model. Parameters for the model are to be found in Table VI. 

Parameters representing the catalyst bed were taken from Briggs et al. (1977,1978) transport coefficients for heat and mass were calculated from well-established correlations, whereas the kinetic parameters came from measurements on Russian catalysts (Ivanov and Balzhinimaev, 1987) of about the same composition as the commercial catalyst used by Briggs. These parameters are collected in Table VI. The model used by Silveston et al. contained, therefore, no adjustable parameters. 

MW-HT techniques can shorten the reaction time. For example, Ivanov et al. [38] synthesized ZnO nanocrystals in 10 min with the assistance of microwave hydro-thermal methods. Huang et al. [39] also demonstrated the use of microwave radiation in the hydrothermal synthesis of ZnO complex nanostructures. These nanocrystals showed high photocatalytic activity in a model reaction of Methyl Orange photodegradation. Li et al. [40] synthesized W03 nanorods in 20 min and showed high... 

Kurshakova, N. N. and Ivanov, A. E. (1963). A model of experimental lung cancer caused by intratracheal introduction of radioactive cerium, Bull. Exp. Biol. Med. USSR 54, 787. 

Ivanov A. N. et al, On pionic hydrogen. Quantum field theoretic, relativistic covariant and model independent approach arXiv nucl-th/0306047. 

The parameters of the model were used for the calculation of the diamagnetic susceptibility Xd and the electron static (low frequency) polarizability a(0) (Ivanov-Smolensky G.A. et al, Acta Cryst. 1983, A39, 411). For ionic bonding and spherical symmetry of atoms the classical Langeuven equation is valid. So with account to the S5mimetry we will obtain ... 

A few years ago, Blagonev and Ivanov described the bis-deprotonation of aryl acetic acids by Grignard reagents. These magnesinm dianions, known as Ivanov reagents, react with aldehydes and ketones. Reaction between dianions of phenylacetic acid and benzaldehyde yields the anti S-hydroxy acid as the major diastereomer anti/syn 69/22) (equation 113). This result is in agreement with the formation of a cyclic chair-like transition state according to the model of Zimmerman-Traxler . 

The present volume is a non-thematic issue and includes seven contributions. The first chapter byAndreja Bakac presents a detailed account of the activation of dioxygen by transition metal complexes and the important role of atom transfer and free radical chemistry in aqueous solution. The second contribution comes from Jose Olabe, an expert in the field of pentacyanoferrate complexes, in which he describes the redox reactivity of coordinated ligands in such complexes. The third chapter deals with the activation of carbon dioxide and carbonato complexes as models for carbonic anhydrase, and comes from Anadi Dash and collaborators. This is followed by a contribution from Sasha Ryabov on the transition metal chemistry of glucose oxidase, horseradish peroxidase and related enzymes. In chapter five Alexandra Masarwa and Dan Meyerstein present a detailed report on the properties of transition metal complexes containing metal-carbon bonds in aqueous solution. Ivana Ivanovic and Katarina Andjelkovic describe the importance of hepta-coordination in complexes of 3d transition metals in the subsequent contribution. The final chapter by Sally Brooker and co-workers is devoted to the application of lanthanide complexes as luminescent biolabels, an exciting new area of development. 

I.A. Ivanov, J. Mitroy, Optical model theory for positron annihilation during scattering, J. Phys. B At. Mol. Opt. Phys. 33 (2000) L831. 

Mekenyan, O.G., Karabunarliev, S.H., Ivanov, J.M., and Dimitrov, D.N., A new development of the OASIS computer-system for modelling molecular properties, Comput. Chem., 18, 173-187, 1994. 

The simple diastereoselectivity of aldol reactions was first studied in detail for the Ivanov reaction (Figure 13.45). The Ivanov reaction consists of the addition of a carboxylate enolate to an aldehyde. In the example of Figure 13.45, the diastereomer of the /1-hydroxycarboxylic acid product that is referred to as the and-diastereomer is formed in a threefold excess in comparison to the. vy/j-diastereoisomer. Zimmerman and Traxler suggested a transition state model to explain this selectivity, and their transition state model now is referred to as the Zimmer-man-Traxler model (Figure 13.46). This model has been applied ever since with good success to explain the simple diastereoselectivities of a great variety of aldol reactions. 

The application of the Zimmerman-Traxler model to the specific case of the Ivanov reaction of Figure 13.45 is illustrated in Figure 13.46. The reaction proceeds preferentially through... 

Fig. 13.46. Explanation of the anti-selectivity of the Ivanov reaction of Figure 13.45 by means of the Zimmerman-Traxler model. The stereodescriptors Re and Si are defined as follows. Suppose you are looking down on the plane of an alkene, in which an sp2-hybridized C atom is connected to three different substituents. You are on the Re side of the double bond if the Cahn-Ingold-Prelog priorities of these substituents decrease going clockwise, and on the Si side otherwise.

Ivanov LI, Oguz T (eds) (1998) Ecosystem Modeling as a Management Tool for the Black Sea. Kluwer Academic Publishers, Netherlands... 

Arkhipkin VS, Ivanov VA, Nikolaenko EG (1987) Modelling of the barothropic seishes in the Southern seas. In Numerical modelling of hydrophysical processes and phenomena in the enclosed basins. Moscow, Nauka p 104 (in Russian)... 

Oguz T, Ivanov LI, Besiktepe S (1998) Circulation and hydrographic characteristics of the Black Sea during 1992. In Ivanov LI and Oguz T (eds) Ecosystem modeling as a management tool for the Black Sea. Kluwer Acad Publ, Dordrecht, The Netherlands, p 69... 

Eremeev VN, Ivanov LI, Samodurov AS, Duman M (1997) Bottom boundary layer in the Black Sea a simple model of formation. In Ozsoy E, Mikaelyan A (eds) Sensitivity to change Black Sea, Baltic Sea and Northern Sea. Kluwer, Dordrecht, p 275... 

Belokopytov V (1998) Long-term variability of cold intermediate layer renewal conditions in the Black Sea. In Ivanov LI, Oguz T (eds) Ecosystem Modeling as a Management Tool for the Black Sea. NATO Science Series. Series 2 Environmental Security 47. Kluwer Academic Publishers, Dordrecht, The Netherlands, p 47... 

The key idea of the Zimmerman-Traxler model is that aldol additions proceed via six-membered ring transition state structures. In these transition states, the metal (a magnesium cation in the case of the Ivanov reaction) coordinates both to the enolate oxygen and to the O atom of the carbonyl compound. By way of this coordination, the metal ion guides the approach of the electrophilic carbonyl carbon to the nucleophilic enolate carbon. The approach of the carbonyl and enolate carbons occurs in a transition state structure with chair conformation. C—C bond formation is fastest in the transition state with the maximum number of quasi-equatorially oriented and therefore sterically unhindered substituents. 

Fig. 10.41. Explanation of the anh-selectivity of the Ivanov reaction of Figure 10.40 by means of the Zimmerman-Traxler model. The...

Bell et al. [33] proposed an analytical formula, widely known in the literature as the Belfast ionization (BELI) formula [34] that contains the dipole interaction term for the electron-impact ionization of atoms and ions. It has been applied to light atomic and ionic targets with species-dependent parameters. Godunov and Ivanov [34] applied the BELI formula to the El ionization of Ne 1 ions. Here also no generality as to parameters of the formula was provided regarding the species-dependent parameters. Moreover, the BELI formula does not make any allowance for relativistic effects. Haque et al. [35-38] have proposed a modification of this BELI model for evaluating the El K-, L-, and M-shell ionization cross sections of atoms. The relativistic and ionic effects are also incorporated in their modified BELI (MBELL) [35-38] model in addition to generalizing the species-independent... 

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