Reaction of phenylphosphine with p-quinones

Conclusions The reaction of phenylphosphine with p-quinones gives the corresponding hydroquinones and diphenyldiphosphine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1660–1661, July, 1978.     

Chemistry of 2,5-bis(trimethylsiloxy) furans. I: Preparation and diels-alder reactions

A number of substituted 2,5-bis (trimethylsioloxy) furans were prepared from the corresponding succinic anhydrides, and were found to be reactive dienes for the Diels-Alder reaction with electron - withdrawing dienophiles, giving p-quinones and hydroquinones.     

Carotenoids of the ascidianHalocynthia aurantium

It has been established that the main components of the carotenoid fraction of an extract ofHalocynthia aurantium are astaxanthin and diatoxanthin, the latter possessing a weak antioxidant activity. No prenylated hydroquinones, which are characteristic for colonial species of ascidians were detected in the four species of solitary ascidians from the Sea of Japan investigated.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 431–433, July–August, 1984.     

Photodynamic effects in the components of cotton seeds

The formation of a stable radical cation and of an unstable peroxide form of gossypol in the light under aerobic conditions has been established on the basis of an analysis of the ESR spectra obtained. The formation of mono- and dianions of gossypol in its alkaline solutions has been shown.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenni, No. 3, pp. 354–360, May–June, 1987.     

Reactions of potassium dibenzo-18-crown-6 pentacyanocobaltate(II) with some lewis bases

ESR has been applied to the interactions of [K(DBC)]₃[Co(CN)₅], in which DBC is dibenzo-18-crown-6, in methanol solution with triphenylphosphine, pyridine, and triethylamine. The ESR spectra are described for the paramagnetic [(NC)₅CoB]^3– adducts, where B is triphenylphosphine or pyridine.Translated from Teoreticheskaya i Éxperimental'naya Khimiya, Vol. 25, No. 2, pp. 234–237, March–April, 1989.     

Membrane-active properties of crambin

A thionin-like protein with M. M. 5kDa has been isolated fromCrambe kotschyana seeds. It has been shown that crambin possesses, a low lytic action on erythrocytes but inhibits the Ca-ATPase of the sarcoplasmic reticulum of rabbit skeletal muscles. A disordering action of crambin on the structures of both the sarcoplasmic reticulum and liposomes has been established by ESR and microcalorimetry.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 82–88, January–February, 1998.     

Study and isolation of vanadylporphyrins from the petroleum oils of the Buzachi peninsula

Summary 1. The vanadylporphyrin complexes of the petroleum oils of the Buzachi peninsula have been studied by the ESR method and spectrophotometrically. The results of the investigation show that the ESR method is the most convenient for determining small amounts of vanadylporphyrins in petroleum oils and extracts.2. The selectivity of various solvents in the extraction of vanadylporphyrin complexes from petroleum oils, as determined by the ESR method, is discussed.Institute of the Chemistry of Petroleum and Natural Salts, Academy of Sciences of the Kazakh SSR, Gur'ev. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 389–392, May–June, 1978.     

Accounting for effects of AZA-substitution on hyperfine interaction constants in ESR spectra

A previously developed scheme for describing the effects of substituents on the physicochemical characteristics of molecules with conjugated bonds has been extended to systems with an open electron shell. The distribution of spin density has been found for a number of anion radicals of azines on the basis of a calculation of their hydrocarbon analogs. The results are in agreement with experimental values of the HFI constant in the ESR spectra of these compounds.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 155–161, March–April, 1989.     

1,4-Bis(phosphine)-2,5-difluoro-3,6-dihydroxybenzenes and their P-oxides: Syntheses, structures, ligating and electronic properties

Reactions of 1,4-difluoro-2,5-dimethoxybenzene with LDA (1:2) at low temperatures generated organodilithio intermediates; quenching the reaction mixtures with chlorophosphines ClPR₂ produced 1,4-bis(phosphino)-2,5-difluoro-3,6-dimethoxybenzenes 1a (R = Ph) and 1b (R = iPr). Demethylation of 1a–b was accomplished by BBr₃, yielding bis(phosphino)hydroquinones 2a–b. Treating 2a–b with excess hydrogen peroxide produced bis(phosphinyl)hydroquinones 3a–b. The binucleating properties of 2a were established by the formation of a bimetallic nickel complex upon reaction with Ph₂Ni(PMe₃)₂. Electrochemical activity of hydroquinones 2a–b and 3a–b was examined by cyclic voltammetry. In addition, compounds 2a, 3a and 3b were obtained in crystalline form and characterized by single-crystal X-ray diffraction. The influence of the fluorine substituents on the composition of the frontier orbitals of 2a and 3a was examined by computational methods.     

Tautomerism in ion pairs of semiquinone anion radicals with ammonium cations

A study has been made of the influence of solvation factors on the kinetics and mechanism of cationotropism in ion pairs of certain semiquinone anion radicals with ammonium cations. It has been shown that the medium influences the magnetic resonance parameters of the ESR spectra of these species.Karaganda University. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 2, pp. 184–188, March–April, 1991. Original article submitted December 15, 1986.     

Complexes of copper with 14–18-membered macrocyclic tetraaza ligands and their participation in oscillating chemical reactions

A number of copper complexes have been synthesized with 14–18-membered tetraaza macrocyclic ligands having six methyl groups and two double bonds located in the cis position relative to the metal ion. These compounds have been investigated by means of ESR spectrometry and electronic and IR spectroscopy. It has been shown that the size of the macroring does not have any great influence on the magnitudes of the spectral parameters. It has been found that these copper complexes can be oxidized by potassium bromate in an oscillatory regime.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 1, pp. 59–64, January–February, 1986.     

PMR study of the degenerate electron transfer between 1,2,3-trimethyl-2-phenylbenzimidazoline and its cation radical

The degenerate electron transfer (electron exchange) between 1,2,3-trimethyl-2-phenylbenzimidazoline and the perchlorate of its radical cation has been studied by PMR in deuteriated aceonitrile. We have determined rate constants and activation parameters for this process, and also some hyperfine interaction (HFI) constants for the cation radical, inaccessible by ESR measurements.Translated from Teoreticheskie i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 658–663, November–December, 1990.     

An investigation of the membranotropic properties of the plant toxin thionin isolated fromPyrularia pubera

It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993.     

Quick method for analysis of anisotropic ESR spectra of particles with a g factor having rhombic symmetry in partially ordered and unordered systems

The exact integral expression describing the form of the anisotropic ESR spectrum of particles with a g factor having rhombic symmetry and a spin S=1/2 has been expanded into a rapidly converging series. This has made it possible to formulate simple rules for the quick analysis of experimental spectra in the case of individual absorption lines with Gaussian and Lorentzian shapes and to determine the corrections associated with the approximate nature of the approach. The rules obtained are universal, i.e., they are equally valid for the ESR spectra of both unordered and partially ordered systems. They can be used to determine the components of the g factor, the width of an individual absorption line, and the orientational distribution functions of the particles in a sample from spectra with sufficient accuracy. The applicability of the expressions obtained has been demonstrated by comparing them with exact computer-simulated ESR spectra.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 6, pp. 738–742, November–December, 1988.     

Mechanism of catalytic hydrogenation of nitrobenzene in an aprotic medium in the presence of quinones

Conclusions The hydrogenation of nitrobenzene in an aprotic medium in the presence of quinones is realized by a reduction-protonation mechanism through alternating stages of electron transfer and protonation. The function of proton donor is fulfilled by the corresponding hydroquinones formed from the quinones under the reaction conditions.Translated from IzvÉstiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1500–1505, July, 1981.     

Metabolites of the pathogenic fungus Verticillium dahliae II. Components of the fraction of neutral lipids from the culture liquid

Summary Di-2-ethylhexyl phthalate has been isolated from the neutral lipids fraction of the culture liquid of the fungusVerticillium dahliae Kleb. Its¹H and¹³C magnetic resonance spectra have been obtained, and an assignment of the signals has been made.On the basis of their UV, IR, and ESR spectra, the chromogenic components of the neutral lipid fractions have been assigned to the melanins.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 689–693, November–December, 1975.     

ESR investigation of the electronic structure of the pentacyanocobaltate(II) anion in solutions

The ESR spectra of the pentacyanocobaltate(II) anion within its salts with Li⁺, Na⁺, K⁺, and [KL]⁺ cations, where L is a macrocyclic polyether, in various solvents have been obtained and analyzed. The spin density in the 3d and 4s orbitals of cobalt and the isotropic hyperfine coupling constants have been calculated. It has been shown that the electronic structure of the pentacyanocobaltate(II) anion is practically independent of the nature of the cation in its salt and the solvent.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 1, pp. 105–110, January–February, 1986.     

ESR study of the 1,2-migration of F atoms in polyfluorinated radicals

The 1,2-migration of the F atom in polyfluorinated cyclohexadienyl radicals generated in the reaction of perfluoro-p-xylene with pentafluorobenzoyl peroxide has been observed directly by ESR.Translated fromIzvestiya Akademii Nauk. Seriya Khitnicheskaya, No. 1, pp. 100–103, January, 1995.     

ESR spectrum of the oxidized vanadylporphyrin complex of Karazhanbass petroleum

As a result of the use of various oxidants, mono- and bications of the natural vanadylporphyrins of Karazhanbass petroleum have been obtained, and their ESR spectra have been studied.Institute of the Chemistry of Petroleum and Natural Salts of the Kazakh SSR Academy of Sciences, Gur'ev. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 190–193, March–April, 1990.     

Theoretical prediction of the hydride affinities of various p- and o-quinones in DMSO

The hydride affinities of 80 various p- and o-quinones in DMSO solution were predicted by using B3LYP/6-311++G (2df,p)//B3LYP/6-31+G* and MP2/6-311++G**//B3LYP/6-31+G* methods, combined with the PCM cluster continuum model for the first time. The results show that the hydride affinity scale of the 80 quinones in DMSO ranges from -47.4 kcal/mol for 9,10-anthraquinone to -124.5 kcal/mol for 3,4,5,6-tetracyano-1,2-quinone. Such a long scale of the hydride affinities (-47.4 to -124.5 kcal/mol) indicates that the 80 quinones can form a large and useful library of organic oxidants, which can provide various organic hydride acceptors that the hydride affinities are known for chemists to choose in organic syntheses. By examining the effect of substituent on the hydride affinities of quinones, it is found that the hydride affinities of quinones in DMSO are linearly dependent on the sum of the Hammett substituent parameters sigma: DeltaGH-(Q) approximately -16.0Sigmasigmai - 70.5 (kcal/mol) for p-quinones and DeltaGH-(Q) approximately -16.2Sigmasigmai - 81.5 (kcal/mol) for o-quinones only if the substituents have no large electrostatic inductive effect and large ortho-effect. Study of the effect of the aromatic properties of quinone on the hydride affinities showed that the larger the aromatic system of quinone is, the smaller the hydride affinity of the quinone is, and the decrease of the hydride affinities is linearly to take place with the increase of the number of benzene rings in the molecule of quinones, from which the hydride affinities of aromatic quinones with multiple benzene rings can be predicted. By comparing the hydride affinities of p-quinones and the corresponding o-quinones, it is found that the hydride affinities of o-quinones are generally larger than those of the corresponding p-quinones by ca. 11 kcal/mol. Analyzing the effect of solvent on the hydride affinities of quinones showed that the effects of solvent (DMSO) on the hydride affinities of quinones are mainly dependent on the electrostatic interaction of the charged hydroquinone anions (QH-) with solvent (DMSO). All the information disclosed in this work should provide some valuable clues to chemists to choose suitable quinones or hydroquinones as efficient hydride acceptors or donors in organic syntheses and to predict the thermodynamics of hydride exchange between quinones and hydroquinones in DMSO solution.