Pyrimidines

3-Arylbenzo[f]quinazolines were obtained by reaction in acetic or propionic acid of -naphthylamine, ammonia, and aromatic aldehydes containing an NR₂ or OH group. A mechanism is proposed for the formation of monoarylbenzo[f]quinazolines from the corresponding intermediate 1,3-diaryldihydrobenzo [f] quinazolines by acid cleavage of the C-aryl bond in the 1 position. This mechanism was confirmed experimentally by establishment of the fact of cleavage of 1,3-bis (p-methoxyphenyl)-1,2-dihydrobenzo[f] quinazoline when the acidity of the medium is increased; 3-(p-methoxyphenyl) benzo [f] quinazoline and anisole were obtained in the reaction products. Condensation in the presence of formic acid gave -arylidene-N-formyl--naphthylamines rather than arylbenzo [f] quinazolines.See [1] for communication LXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1265–1271, September, 1978.     

Cucurbituril as a new “host” of organic molecules in inclusion complexes

The latest data concerning the study of inclusion complexes based on cucurbiturils as a new class of molecular hosts are generalized in the review. The methods of synthesis, the structure, and physical and chemical properties of cucurbiturils are considered. Special attention is given to the discussion of the principles of construction of supramolecular complexes. The factors affecting stability, composition, and structure of inclusion complexes are considered. The potential applications of cucurbituril as molecular containers for a number of photochemical reactions are given. Advantages of using this class of compounds in comparison with other known cavitands are presented.     

Active parametric identification of stochastic linear discrete systems in the frequency domain

Under consideration are some theoretical and applied aspects of the active identification of the multidimensional stochastic linear discrete systems in the frequency domain which are described by models in the state space. Original results are obtained in the case that the parameters of mathematical models to be estimated appear in various combinations in the state and control matrices, as well as in the perturbation matrix and the covariation matrices of the dynamic noise and measurement errors. By an example of a system controlling a boring machine, the efficiency and sensibility is shown of applying the active identification procedure.     

Platinum–nickel alloy catalysts for fuel elements

Within the framework of the methods of the electron density functional and the ab initio pseudopotential, the spatial distributions of density of valence electrons and the electron energy spectra were obtained for platinum-based films with supplement atoms of the second metal, action of mechanical stress and oxygen atoms. The most critical factors for increase of the catalyst activity during oxidization of methanol are mechanical stress and dissociated oxygen.     

On Stability of Integral Sets of Impulsive Differential Systems

We introduce the notion of stability of integral sets of impulsive differential systems of general form (with nonfixed times of impulse influence). We establish conditions sufficient for the stability of an integral set.     

Aggregative behavior of AB and ABC block copolymers in the solid phase and in a nonselective solvent

Effects of the amount of chemically dissimilar blocks (two or three) and their polarity on the aggregative behavior of АВ and АВС linear block copolymers of various compositions that are based on polystyrene, poly(n-butyl acrylate), and either poly(acrylic acid) or poly(tert-butyl acrylate) in bulk and in the nonselective solvent DMF are studied via differential scanning calorimetry and dynamic light scattering. АВ block copolymers composed of two chemically dissimilar blocks in the diluted solution in DMF are fully dispersed into macromolecular coils. However, the simultaneous incorporation of three incompatible blocks of different polarities (polystyrene, poly(acrylic acid), and poly(n-butyl acrylate)) into the copolymer is accompanied by a well-defined segregation of blocks in the nonselective solvent, regardless of the composition of the block copolymer and the length and sequence of blocks. This phenomenon makes itself evident as the formation of intermacromolecular aggregates in diluted solutions with a mean hydrodynamic radius of 60–120 nm that are stable in the range 10–60°C. A decrease in the level of the thermodynamic incompatibility of blocks (replacement of a poly(acrylic acid) polar block with a less polar poly(tert-butyl acrylate) block) or the selective improvement of solvent quality with respect to the polar block (the addition of LiBr to DMF) suppresses the segregation of blocks and may lead to the formation of a molecularly dispersed solution of the block copolymer.     

Free-radical polymerization of methyl methacrylate in the presence of dithiobenzoates as reversible addition-fragmentation chain transfer agents

The pseudoliving radical polymerization of methyl methacrylate in bulk mediated by dithiobenzoates with various leaving groups as reversible addition-fragmentation chain-transfer agents has been studied. It has been shown that polymerization proceeds under conditions of the low steady-state concentration of radical intermediates; as a result, the steady-state of the process is rapidly achieved even at low conversions. Retardation of polymerization observed at high concentrations of reversible addition-fragmentation chain-transfer agents is apparently associated with the occurrence of chain termination reactions involving intermediates, as evidenced by the model reaction. The autoacceleration of polymerization is suppressed with an increase in the concentration of reversible addition-fragmentation chain-transfer agents. An efficient approach to the synthesis of a narrow-dispersed PMMA with the controlled molecular mass has been suggested.     

On the Asymptotics of Solutions of the Second-Order Differential Equations with Rapidly Varying Nonlinearities

Ukrainian Mathematical Journal - We establish new results concerning the conditions of existence of one class of monotonic solutions of a two-term nonautonomous differential equation of the second...