Acceleration of the Passerini reaction in the presence of nucleophilic additives

An accelerating effect of nucleophilic additives was revealed for the Passerini multi-component reaction. The influence of aqueous solutions on the reaction rate was studied in detail and the direct involvement of water in the bond-making step was attributed as the basis of an accelerating effect. Other nucleophiles were tested as alternatives to water; as a result N-hydroxysuccinimide is proposed as an accelerant of the Passerini reaction.     

Acid-catalyzed oligomerization of aromatic ethers (Rolivsans) with terminal styrene and methacrylate groups

Cationic mechanism of transformation of unsaturated aromatic monomers contained in Rolivsans into thermosetting aromatic oligoethers with increased molecular weight was analyzed. The composition and chemical structure of Rolivsans as influenced by catalytic systems with various donor-acceptor properties were studied.     

IR spectral study of the effect of the reaction medium on the state of cobalt in a 10% Co/Al2O3 catalyst for aliphatic hydrocarbons from CO and H2

Diffuse scattering IR spectroscopy was used to study the 10% Co/Al₂O₃ catalyst for the synthesis of aliphatic hydrocarbons from CO and H₂. Ionic and metallic cobalt forms were identified in the IR spectroscopy. The adsorption of CO on these forms is accompanied by the appearance of linear and bridged complexes. After prolonged treatment of the catalyst by a CO + 2H₂ mixture, the ions and surface of metallic cobalt remain available for the adsorption of CO. Modification of the surface of metallic cobalt occurs upon the action of the reaction medium. This modification is seen in a bathochromic displacement of the IR bands for the adsorbed and linear CO forms. This displacement is accompanied by a reduction in the strength of the metal-carbon bond in the Co^o-CO complex.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2640–2643, November, 1990.     

Intramolecular hydrogen bond in substituted 3-hydroxypyridines

To explain the character of the intramolecular hydrogen bond in substituted 3-hydroxypyridines, the chemical shifts in the NMR spectra of the hydroxyl group and the IR spectra were studied. It was established that the stability of the intramolecular hydrogen bond of the O-HNR₂ type in substituted 3-hydroxypyridines increases when compared with the corresponding phenols, while an opposite pattern is observed for bonds of the O-H0₂ N type. An approximate evaluation of the energy of the intramolecular hydrogen bond in substituted 3-hydroxypyridines was achieved. When reacting with bases of the same strength, 3-hydroxypyridine forms more stable complexes than phenol.     

Tautomerism of anthraquinones: V. 1,5-Dihydroxy-9,10-anthraquinone and its substituted derivatives

1,5-Dihydroxyanthraquinone and its substituted derivatives are capable of existence in the states structurally described as 9,10-, 1,10-, and 1,5-quinoid tautomerism, and as rotational isomerism involving a cleavage of intramolecular hydrogen bond. 1,5-Quinoid tautomers are characteristic only of substituted derivatives, and also appear in some metal complexes. The considerable color changes on introducing into the 1,5-dihydroxy-anthraquinone methyl, methoxy, and sulfo groups are caused by the shift in tautomeric and conformer equilibria.     

Kinetics of inactivation and effects of stabilization of chloroplasts

The kinetics of inactivation of the electron transport chain of isolated chloroplasts was investigated. Methods for the stabilization of chloroplasts were developed. The mean operating time of the system was increased by a factor of about 200.     

Inclusion of Two PhP(O)(OH) 2 Guest Molecules into the Cavity of Macrocyclic Cavidand Cucurbit[8]uril

A new inclusion compound which is a supramolecular adduct of cucurbit[8]uril with two guest molecules of phenylphosphonic acid, PhP(O)(OH)₂, included into the cavity as ``two guests in host'' is reported. The guests match both size and hydrophilicity/hydrophobicity requirements. Two phenyl groups of molecules of PhP(O)(OH)₂ are directed toward the center of the large hydrophobic cavity whereas the PO(OH)₂ groups are outward-looking and bound with each hydrophilic portal of cucurbit[8]uril by a short hydrogen bond.     

Error distribution in sampled-data measurements

Joint error distributions are estimated for sampled-data measurements.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 73, pp. 66–70, 1992.     

Core-shell nanostructures from single poly(N-vinylcaprolactam) macromolecules: stabilization and visualization

Formation of core-shell poly(N-vinylcaprolactam) (PVCL) single-molecule nanostructures due to interaction of PVCL with metal ions was studied using transmission electron microscopy, 13C NMR, and light scattering. This study demonstrates that addition of CoCl2 to PVCL in its globular conformation yields unimolecular core-shell polymer particles with the core decorated with Co(II) ions. The crucial condition for formation of well-defined unimolecular nanostructures is the presence of stable globular aggregates in aqueous solution. Moreover, the metal ions should have a sufficiently high coordination number (higher than 2) to provide a cross-linking and stabilization of the core.     

Synthesis and study of polydentate ligands that contain a pyrimidine ring

The corresponding hydrazones, azo compounds, and 2,4-bis(1H-pyrazol-1-yl)pyrimidines were synthesized by the reaction of 5-ethyl-2-hydrazino-6-methyl-4(3H)-pyrimidinone, 2-(N-p-butylanilino)-4-hydrazino-6-methylpyrimidine, and 4-hydrazino-2-(1H-pyrazol-1-yl)pyrimidines with salicylaldehyde, isatin, -naphthoquinone, phenanthrenequinone, and acetylacetone. The structures of the synthesized compounds are discussed on the basis of a study of their electronic, IR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1687, December, 1980.