Application of the generalized principle of maximum overlap to the study of the stereochemistry of β-elimination reactions

The dependence of the degree of charge transfer in substituted alkanes on the relative positions and electron-donor (or acceptor) properties of the groups eliminated in -elimination reactions has been studied. Rules obtained from the generalized principle of maximum overlap have been used for the analysis of the relations between the coefficients in front of the basis functions in the expansions of the MOs. It has been established that trans elimination is observed in the case of substituents with pronounced electron-acceptor and electron-donor properties. In heterogeneous-catalytic reactions the nature of the active sites on the surface of the catalyst strongly influences the electron-donor (or acceptor) properties of the groups being eliminated. The catalytic dehydrochlorination of 1,1,2-trichloroethane has been considered as an example.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 2, pp. 168–174, March–April, 1986.     

Quasi-energy statistics for regular and chaotic regimes in quantum systems with Hamiltonians periodic in time

Quantum mechanical systems with Hamiltonians varying periodically in time are considered. It is assumed that the spectrum of the Floquet operator has no absolutely continuous part and spacings between quasi-energies may be statistically described by means of a continuous density. It is shown that the induced statistical density of spacings between fractional parts of the quasi-energies defined with respect tomod (w), suitably normalized, approaches arbitrarily close to an exponential distribution when the number of levels is infinitely increased. This result does not depend on the original distribution. An alternate method of statistically describing fractional parts is proposed which makes it possible to distinguish between the original quasi-energy distribution laws for regular and chaotic regimes.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 108, No. 3, pp. 431–447, September, 1996.     

Compound-specific isotope analysis of benzotriazole and its derivatives

Compound-specific isotope analysis (CSIA) is an important tool for the identification of contaminant sources and transformation pathways, but it is rarely applied to emerging aquatic micropollutants owing to a series of instrumental challenges. Using four different benzotriazole corrosion inhibitors and its derivatives as examples, we obtained evidence that formation of organometallic complexes of benzotriazoles with parts of the instrumentation impedes isotope analysis. Therefore, we propose two strategies for accurate $\delta^{13}$ C and $\delta^{15}$ N measurements of polar organic micropollutants by gas chromatography isotope ratio mass spectrometry (GC/IRMS). Our first approach avoids metallic components and uses a Ni/Pt reactor for benzotriazole combustion while the second is based on the coupling of online methylation to the established GC/IRMS setup. Method detection limits for on-column injection of benzotriazole, as well as its 1-CH $_{3}$ -, 4-CH $_{3}$ -, and 5-CH $_{3}$ -substituted species were 0.1–0.3 mM and 0.1–1.0 mM for δ¹³C and δ¹⁵N analysis respectively, corresponding to injected masses of 0.7–1.8 nmol C and 0.4–3.0 nmol N, respectively. The Ni/Pt reactor showed good precision and was very long-lived ( $>$ 1000 successful measurements). Coupling isotopic analysis to offline solid-phase extraction enabled benzotriazole-CSIA in tap water, wastewater treatment effluent, activated sludge, and in commercial dishwashing products. A comparison of $\delta ^{13}$ C and $\delta ^{15}$ N values from different benzotriazoles and benzotriazole derivatives, both from commercial standards and in dishwashing detergents, reveals the potential application of the proposed method for source apportionment.     

Complex Formation by Galacturonic Acid with Copper(II) and Neodymium(III) Ions in Water Solution

Complex formation by galacturonic acid with copper(II) ion in water solution is studied by themethods of EPR spectroscopy. At the pH > 3 the EPR signal (g 2.174) confirms the complex formation at theligand carboxylic group. The following complex formation parameters are measured: equilibrium constant'g factor, hyperfine coupling constant, average complex lifetime. From the data of electron spectra invisible region the complex composition and stability constant is defined for copper(II) and neodymium(III).     

Monobromination of benzisatins

The monobromination of isomeric benzisatins and tetrahydrobenzisatins was studied. The structure of the products was demonstrated by ¹H NMR spectroscopy. A CNDO/S calculation was carried out for the electronic structure of the starting compounds. The calculated data correctly predict the direction of the bromination with the exception of benz[e]isatin.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 6, pp. 744–748, November–December, 1987.     

Electrochemical Synthesis of Complex Compounds of Transition Elements with Carboxyl- and Carbonyl-containing Ligands

Complex compounds of d- and f-elements with carboxyl- and carbonyl-containing ligands were synthesized by the electrochemical method. The influence exerted by a number of factors on the process course was studied. The dependence of the electrosynthesis parameters on the composition of the forming compounds was established. The composition of these compounds was determined. A new method for anodic synthesis of these compounds was developed.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 6, 2005, pp. 918–923.Original Russian Text Copyright © 2005 by Frolov, Bolotin, Panyshkin.     

Influence of Initial Conditions on the Postcritical Behavior of a Nonlinear Aeroelastic System

The behavior of a nonlinear, non-Hamiltonian system in the postcritical (flutter) domain is studied with special attention to the influence of initial conditions on the properties of attractors situated at a certain point of the control parameter space. As a prototype system, an elastic panel is considered that is subjected to a combination of supersonic gas flow and quasistatic loading in the middle surface. A two natural modes approximation, resulting in a four-dimensional phase space and several control parameters is considered in detail. For two fixed points in the control parameter space, several plane sections of the four-dimensional space of initial conditions are presented and the asymptotic behavior of the final stationary responses are identified. Amongst the latter there are stable periodic orbits, both symmetric and asymmetric with respect to the origin, as well as chaotic attractors. The mosaic structure of the attraction basins is observed. In particular, it is shown that even for neighboring initial conditions can result in distinctly different nonstationary responses asymptotically approach quite different types of attractors. A number of closely neighboring periodic attractors are observed, separated by Hopf bifurcations. Periodic attractors also are observed under special initial conditions in the domains where chaotic behavior is usually expected.