Strahlungschemie von Kohlenwasserstoffen. 16. Mitteilung. Benzol-Brombenzol

The decrease of the concentration of bromobenzene and the formation of biphenyl and bromobiphenyl have been studied in the system benzene-bromobenzene under the influence of γ-rays. Bromobenzene is in competition with its own products for the reactive state of benzene or it can transfer its energy to its products. The rate of this transfer to decomposition is 74 l/Mol. With the help of additives it has been shown that they can act in two ways: firstly they compete with bromobenzene for an activated state of benzene in a reaction that does not depend on temperature. The nature of this activated state has not been determined. Secondly they scavenge phenyl radicals that have been formed in about 70% of the decomposed bromobenzene molecules. This yield depends slightly on temperature. The relative reactivities compared to bromobenzene for the first case and to benzene in the second have been determined as follows: naphthalene (0.6; 23); anthracene (5.8; 800); benzophenone (0.5; 17); cyclohexene (-; 20); N₂O (0.018; -); NO (1.7; 250); O₂ (-; 3400). Naphthacene in benzene is strongly decomposed in the presence of bromobenzene, but it also enhances the decomposition of the latter.     

Alkaloids ofOxytropis. III. Trichophydine

A new alkaloid, which has been named trichophydine, has been isolated from the epigeal part ofOxytropis trichophysa growing in Mongolia. On the basis of the spectral characteristics of the hydrochloride, the structure of 2-O-benzoyl-2(β)-phenylethylamine, which has been synthesized previously, has been established for trichophydine.     

E.S.R. of hydrazoxyl radicals: Evidence for conformational isomers.

Thermolysis of azocarboxylates has been investigated by e.s.r. Experimental evidence for the existence of conformational isomerism in acylnitroxides has been obtained.     

Carbohydrates of allium IX. Polysaccharides of A. suvorovii

The carbohydrate compositions of all the organs ofAllium suvorovii Rgl have been determined and it has been established that the bulk of the fructose accumulates in its bulbs. The dynamics of the accumulation of glucofructans in the bulbs has been studied and it has been found that this accumulation is a maximum in the dormancy stage.     

Rubbing-induced surface textures in nematic MBBA layers and their behaviour under applied d.c. or a.c. voltages

Surface irregularities (for example, rubbing-induced domains, and bumps) have been observed in MBBA nematic cells after special treatment of the electrodes using a conventional soap. Various techniques such as polarizing microscopy, the shadowgraph technique and computer processing of the images have been used. The behaviour of the rubbing-induced domains under a.c. or d.c. electric fields has been studied. A new flexoelectric effect has been observed leading to the dividision of the rubbing-induced domains. A simple model has been proposed (a modification of the Saupe model), which explains the structure and dividision of the rubbing-induced domains.     

Rubbing-induced surface textures in nematic MBBA layers and their behaviour under applied d.c. or a.c. voltages

Surface irregularities (for example, rubbing-induced domains, and bumps) have been observed in MBBA nematic cells after special treatment of the electrodes using a conventional soap. Various techniques such as polarizing microscopy, the shadowgraph technique and computer processing of the images have been used. The behaviour of the rubbing-induced domains under a.c. or d.c. electric fields has been studied. A new flexoelectric effect has been observed leading to the dividision of the rubbing-induced domains. A simple model has been proposed (a modification of the Saupe model), which explains the structure and dividision of the rubbing-induced domains.     

Cyclohexene-sulfur bichloride adducts.: Stereochemical considerations.

The reaction of sulfur dichloride with cyclohexene produces two isomeric trans-adducts of meso and dl configurations. Derivatives of both series have been obtained and configurations have been assigned by means of pseudoasymmetry. General principles for the conformational analysis of systems which contain two inverting 6-membered rings have been discussed and the positions of conformational equilibria have been evaluated. The new conformational effect-stabilization of “heteroconformer”—has been found in the case of dl-bis(2-chlorocyclohexyl) sulfoxide.     

Some N.M.R. experiments using lyotropic nematic liquid crystals

A series of lyotropic nematic liquid crystals based on aniso-dimensional micelles can be subdivided according to micelle shape and diamagnetic susceptibility anisotropy. The proton magnetic resonance spectra of benzene dissolved in dilute solution in several of these phases have been analysed. The signs of the partially averaged dipole-dipole coupling give information about the relative alignment of the six-fold symmetry axis of benzene, the director and the magnetic field. The system caesium perfluorooctanoate/water is unusual in two respects. The system forms a nematic phase with only a binary mixture and the disk micelles align in a perpendicular plane to the magnetic field. As a result the binary system has been studied previously in some detail (see N. Boden, S. A. Come and K. W. Jolley, 1987, J. phys. Chem.91, 4092). New measurements on the interesting phase diagram have been accomplished using caesium-133 and deuterium magnetic resonance measurements at various temperatures. Some dilatometric measurements have been made to complement the N.M.R. studies.     

Photochemistry of imidazolides. I. The photo-Fries-type rearrangement of N-substituted imidazoles.

A number of N-substituted imidazoles 1a–1i have been found to photo-isomerize to give the corresponding 2-substituted- and 4(or 5)-substituted imidazoles ( 2a–2i and 3a–3i ). The role of a dissociative path in these reactions has been demonstrated.     

Quantitative theory of iniferter polymerization. I. Kinetics

On the basis of a rather general scheme of elementary reactions of radical polymerization conducted in the presence of iniferters, kinetic equations have been derived describing this process over the whole range of monomer conversion. Proceeding from thorough analysis of these equations, different regimes of polymerization have been found that differ in values of order with respect to the iniferter and monomer of the initial rate of polymerization. Conditions for kinetic parameters have been formulated whose fulfillment predetermines that radical polymerization occurs according to the iniferter mechanism. © 1994 John Wiley & Sons. Inc.     

Some physical properties of polyorganosiloxanes. I. Linear polyorganosiloxanes

Some physical properties of linear polydimethylsiloxanes have been studied. The states and transitions in polydimethylsiloxanes have been investigated by using the method of dynamic heat capacity and a thermomechanic method in the temperature range from ?150 to +200°C. The temperature dependence of primary and secondary crystallization has been studied by optical, calorimetric, and x-ray methods.     

Diterpenoids ofPulicaria salviifolia. III. The structure of salvicinin

The new diterpene acid salvicinin has been isolated from the epigeal part ofPulicaria salviifolia and its structure has been established as 15-acetoxy-6α-hydroxy-trans-cleroda-3,13-dien-19-oic acid. A capacity of salvicinin for undergoing lactonization in the presence of acetic anhydride has been revealed, and the lactone formed has been isolated and chracterized.     

Carbohydrates ofAllium. IV. Glucofructans ofAllium longicuspis

Water-soluble polysaccharides have been isolated from the bulbs ofAllium longicuspis Rgl. By fractionating the combined water-soluble polysaccharides, homogeneous polysaccharides with molecular weights of 15,500 and 5100 have been isolated. It has been shown by spectral and chemical methods that they consist of glucofructans of a mixed type containing glycosidic bonds of the inulin (2 → 1) and levan (2→6) types in a ratio of 2.1:1.     

29Si N.M.R. investigations of polysiloxanes

A number of side chain liquid crystal polysiloxanes prepared from both homo-and co-polymeric backbones have been studied by ²⁹Si N.M.R. and the chemical shifts assigned. Partly mesogenated poly(hydrogenmethylsiloxanes) have been similarly studied and chemical shift assignments made for sequence distributions. The data should prove helpful in studies of compositional variation in preparations of side chain copolymeric polysiloxanes.     

Carbohydrates of allium IX. Polysaccharides of A. suvorovii

The carbohydrate compositions of all the organs ofAllium suvorovii Rgl have been determined and it has been established that the bulk of the fructose accumulates in its bulbs. The dynamics of the accumulation of glucofructans in the bulbs has been studied and it has been found that this accumulation is a maximum in the dormancy stage.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedienii, No. 6, pp. 622–624, November–December, 1992.     

Some N.M.R. experiments using lyotropic nematic liquid crystals

Abstract

A series of lyotropic nematic liquid crystals based on aniso-dimensional micelles can be subdivided according to micelle shape and diamagnetic susceptibility anisotropy. The proton magnetic resonance spectra of benzene dissolved in dilute solution in several of these phases have been analysed. The signs of the partially averaged dipole–dipole coupling give information about the relative alignment of the six-fold symmetry axis of benzene, the director and the magnetic field. The system caesium perfluorooctanoate/water is unusual in two respects. The system forms a nematic phase with only a binary mixture and the disk micelles align in a perpendicular plane to the magnetic field. As a result the binary system has been studied previously in some detail (see N. Boden, S. A. Come and K. W. Jolley, 1987, J. phys. Chem. 91, 4092). New measurements on the interesting phase diagram have been accomplished using caesium-133 and deuterium magnetic resonance measurements at various temperatures. Some dilatometric measurements have been made to complement the N.M.R. studies.     

Solute-Solvent Interactions : Vol. 2. Editors J.F. Coetzee and C.D. Ritchie. Marcel Dekker Inc., New York, 1976, xii + 459 pages,Sfr. 125.

The photoelectron spectra of eight 4 π-electron hydrocarbons and their tricarbonyl complexes have been measured. From these spectra the perturbation energies of the π orbitals introduced by the tricarbonyliron moiety have been determined. These perturbation energies are 0.89 ± 0.07 and 0.22 ± 0.06 eV for the first and second π orbitals, respectively. Given these perturbation energies and the photoelectron spectra of the tricarbonyliron complexes of cyclobutadiene and trimethylenemethane, π-ionization energies for the two transients, cyclobutadiene (8.29 and 11.95 eV) and trimethylenemethane (8.36 and 11.79 eV), have been predicted.     

Alkaloids ofOxytropis. III. Trichophydine

A new alkaloid, which has been named trichophydine, has been isolated from the epigeal part ofOxytropis trichophysa growing in Mongolia. On the basis of the spectral characteristics of the hydrochloride, the structure of 2-O-benzoyl-2()-phenylethylamine, which has been synthesized previously, has been established for trichophydine.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, FAX (3712) 62 73 48. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 414–416, May–June, 1994.     

Finite jellium models. I. Restricted Hartree-Fock calculations

Restricted Hartree-Fock calculations have been performed on the Fermi configurations of n electrons confined within a cube. The self-consistent-field orbitals have been expanded in a basis of N particle-in-a-box wave functions. The difficult one- and two-electron integrals have been reduced to a small set of canonical integrals that are calculated accurately using quadrature. The total energy and exchange energy per particle converge smoothly toward their limiting values as n increases; the highest occupied molecular orbital-lowest unoccupied molecular orbital gap and Dirac coefficient converge erratically. However, the convergence in all cases is slow.     

ESR spectra of trimeric heteronuclear clusters. I. Theory

A theory of the ESR spectra of trimeric heteronuclear clusters consisting of transition-metal ions has been developed. The theoretical model includes both isotropic exchange and Dzialoshinskii—Moriya antisymmetric interactions; it also takes into account the differences between g values of the individual ions. The energy levels of the interacting multielectronic ion system in a magnetic field have been found in theory. Radiofrequency transition probabilities have been determined for the canonical directions of the field. It is shown that the ESR spectrum exhibits peculiarities closely related to the non-linear behaviour of Zeeman levels.