Analytical Azo Coupling Reactions: A Quantum-Chemical Consideration

Azo coupling reactions of 1-aminonaphthalene with naphthalene-1-diazonium and 4-sulfobenzene-diazonium cations are studied by quantum chemistry. It is found that the reactions are orbital controlled and their regioselectivity is unambiguously governed by the thermodynamic properties of the intermediate σ-complexes and by the effect of the aqueous medium. The latter causes high site selectivity, providing the choice of one of the two possible reaction channels predicted on the basis of quantum-chemical calculations of the isolated molecular systems. As a result, azo coupling occurs at the 4-position of the 1-aminonaphthalene molecule. Additionally, the aqueous medium provides the selection of analytical forms, namely, the protonated azo coupling products that have the quinone-hydrazone structure. On the basis of the quantum-chemical study, the analytical performances of the two azo coupling reactions mentioned above are discussed.     

Cyclocondensation of [1-Cyano-2-(methylsulfanyl)vinyl]triphenylphosphonium Iodide with Amidine Nucleophiles

The substituted vinylphosphonium salt (E)-MeSCH=C(CN)P⁺Ph₃I⁻ readily cyclizes under the action of benzamidine and 3-amino-s-triazole, but it does not enter cyclocondensation with 2-aminopyridine. The structure of the cyclization product with 3-amino-s-triazole was confirmed by its transformation to 7-imino-6-(triphenylphosphoranylidene)-6,7-dihydro-s-triazolo[1,5]pyrimidine which was identified by X-ray diffraction. This stabilized ylide and its analogs proved useful starting materials for regioselective syntheses of 2-R-4-alkyl-4,7-dihydro-s-triazolo[1,5-a]pyrimidin-7-ones.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 565–570.Original Russian Text Copyright © 2005 by Smolii, Muzychka, Chernega, Drach.     

Electron impact mass spectral interpretation for some thiophosphoryl-p-acetylaminobenzenesulfonamides

This work discusses the synthesis and the fragmentation patterns for 2-(p-acetylaminosulfonamido)-2-thiono-(5,5-dimethyl-1,3,2-dioxaphosphorinane)(1) and for the p-acetylaminosulfonylamides of O,O-diethylthiophosphoric acid (2), O,O-diphenylthiophosphoric acid (3), dimethylaminocyclohexylthiophosphoric acid (4), and diethylaminophenylthiophosphoric acid (5). A thionamidic-thiolimidic structure was attributed to compounds 1-5, consistent with their IR and NMR spectra. EI mass spectra at 70 eV, high resolution (HR) mass measurements and metastable ion spectra were used to elucidate the fragmentation processes and to determine the kinetic energy release values associated with the metastable ion dissociations. HR accurate mass measurements were used to confirm the compositions of the more abundant ions.     

Spectrophotometric determination of bismuth after extraction of hexadecyltributylphosphonium tetraiodobismuthate(III) by microcrystalline benzophenone

Bismuth (0–110 μg) is determined spectrophotometrically at 495 nm after its adsorptive extraction from dilute sulphuric acid as hexadecyltributylphosphonium tetraiodobismuthate(III) on microcystalline benzophenone and dissolution of the solid phase in carbon tetrachloride. The effects of acidity, diverse ions and masking studies are reported. The system is applied to the determination of bismuth in pharmaceutical samples.     

Dependence of the reactivity of allophanates on the conformation of the main chain

The CNDO/2 method was used to investigate the conformation and structure of alkylsubstituted allophanates. The possibility of the existence of isomers both with coplanar and with noncoplanar main chains NCNC was studied. It was shown that the formation of conformers with a cis-structure of the ester group is more probable. On the basis of an analysis of the dependence of the reactivity on the structure of the main chain, hypotheses were advanced on the role of the more stable conformers in various channels of polyaddition of isocyanates.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 3, pp. 360–363, May–June, 1986.     

Chemistry of 1,5-diketone derivatives. 1. Oxidation of 8a-methoxy-4a,5,6,7,8,8a-hexahydrochromenes by monoperphthalic acid

2-(2-Oxo-3-hydroxy-1,3-diphenylpropyl)cyclohexanone, 2-(2,3-dioxo-1,3-diphenylpropyl)cyclohexanone, and 2-benzyl-7a-hydroxy-3-phenylperhydrobenzofuran are formed by the action of monoperphthalic acid on 8a-methoxy-2,4-diphenyl-4a,5,6,7,8,8a-hexahydrochromene. Under analogous conditions, 4a-methoxy-10-phenyl-1,2,3,4, 4a,6,7,8,9,10a-decahydroxanthene forms 7a-hydroxy-3-phenyloctahydrobenzo[b]furan-2-spiro-1-cyclohexan-2-one and its dehydration product. The behavior of the compounds obtained toward acetic anhydride and a methanolic solution of HCl was studied. The configurations of the reaction products and the reaction path are considered.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 177–181, February, 1985.     

Improved short-lived nuclide activation analysis

A novel technique has been developed to increase the sensitivity, precision and accuracy of short-lived nuclide activation analysis and especially of delayed fission neutron counting, by improving the counting statistics. This has been achieved by approaching the irradiated sample to the detector during the counting period in order to compensate for the rapid radioactive decay by variation of the counting efficiency, permitting prolongation of the counting period with constant count rate. The sample holder movement with approximately exponentially decreasing velocity is implemented by a variable DC motor with a rotary to linear movement converter, which is being replaced by a more reliable stepping motor.     

Production of new lagochilin derivatives

The tetrahydric alcohol Lgochilin belongs to the 9,13-epoxylabdane series of diterpenoids. It is produced by many species of plants of the Lagochilus genus and can be used as the starting material for the synthesis of new compounds with a broad spectrum of physiological action [1, 2]. Many lagochilin derivatives possess hemostatic (3, 4) and antiviral properties. Lagochilin derivatives with aromatic hydroxaldehydes and naphthaldehydes have been synthesized, and the cytotoxic effects of the compounds synthesized in cell cultures have been studied.Tashkent State University, (fax (3712) 46 24. 42. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 86–88, January–February, 1995. Original article submitted October 17, 1994.     

Influence of cation structure on decomposition of diacyl peroxides activated by chloride salts of amines

A kinetic study has been made of the interaction of benzoyl peroxide with a number of chloride salts of amines. It is shown that a change of the cation in quaternary ammonium salts does not have any significant effect on the kinetic parameters of the reaction. By means of NMR spectroscopy it has been determined that the structure of the NR₄ ⁺ cation does not change during the course of the reaction. The role of the cation in the process of activation of a diacyl peroxide by chloride salts of amines has been investigated by means of MNDO calculations.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 324–328, July–August, 1992.     

L-asparaginase bound in a polyacrylamide gel

Summary The enzyme L-asparaginase fromE. coli has been included in polyacrylamide gel, and some of its properties have been investigated: stability, pH dependence, heat stability, K_m. It has been shown that the enzymegel obtained has a better stability then the native enzyme.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 382–384, May–June, 1976.