Beiträge zur Massenspektrometrie der Gelsemium-Alkaloide

Zusammenfassung Von den Nebenalkaloiden vonGelsemium sempervirens (L.) Ait. konnte eine Verbindung, zunächst als Gelsemium-Alkaloid A bezeichnet, in reiner Form dargestellt und ihre Konstitution als N-1-Methoxygelsemin aufgeklärt werden. Für die Strukturermittlung erwies sich die Massenspektrometrie als besonders wertvoll. Die Massenspektren einiger Gelsemiumalkaloide sind wiedergegeben, die Fragmentierung dieser Verbindungen wird diskutiert.Au\erdem wurde eine größere Anzahl neuer Basen in kleiner Menge nachgewiesen.

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Contributions to mass-spectrometry of gelsemium-alkaloids (The structure of gelsemium-alkaloid A)

From the minor alkaloids ofGelsemium sempervirens (L.) Ait., one compound, preliminary designated as Gelsemiumalkaloid A, could be isolated and was identified as N-1-Methoxy-gelsemine. For the structure-elucidation mass-spectrometry has been proven to be of great value. Mass spectra of some Gelsemium-alkaloids are reported and the fragmentation of these compounds is discussed.There were further detected a quantity of new alkaloids in small amounts.

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Anmerkung bei der Korrektur (23.10.1972): Während der Drucklegung dieser Arbeit erschien eine Publikation vonE. Wenkert u. Mitarb. [Exper.28, 377 (1972)], in der die Struktur des Gelsevirins als N-1-Methoxy-gelsemin angegeben wird; somit ist Gelsemium-Alkaloid A offensichtlich mit Gelsevirin identisch. Eine solche Identifizierung was uns nicht möglich, da einerseits kein authentisches Präparat von Dr.Marion verfügbar was (Brief von Dr.Edwards, Ottawa, vom 21.6.1971) und andrerseits die wenigen, bisher veröffentlichten Daten über Gelsevirin hierfür nicht ausreichen.     

X-ray spectra and electronic structure of several ternary chalcogenides and their solid solutions

The electronic energy structure of substitution solid solutions CuGa(S_xSe_1−x)₂ is studied within wide limits of sulfur concentration x in the onion sublattice. The SK absorption spectrum is calculated for CuGaS₂ in a high-order multiple scattering approximation using the FEFF7 program. For all concentrations x, partial densities of states are calculated in a full multiple scattering approximation by the local coherent potential method. The calculation schemes for the filled and vacant states are employed, which differ in a choice of the crystalline potential. The effect of a vacancy on the SK level on the density of the free Sp states is considered. The theoretical K absorption spectra and densities of states of CuGaS₂ are compared with the experimental X-ray and X-ray photoelectron spectra. The calculated curves are in good agreement with the experiment. It is established that the densities of the S and Se p states change smoothly with varying concentration of anions. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 6, pp. 1076–1082, November–December, 1998.     

Vibronic properties of 2-azaanthracene and its derivatives

We report an experimental and theoretical (PPP method) study of the UV absorption spectra of 2-azaanthracene and four of its methyl-substituted derivatives. We find that the p bands of these compounds consist of two different vibronic ^* bands. Our experimental and theoretical results suggest a rule for evaluating the effect of methyl groups on ^* transition energies as a function of the charge on the atoms. We interpret the reasons for the different effects of a polar solvent and hydrogen bonding on the ^* bands of these compounds.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 7–15, June, 1977.     

H, C NMR spectral and single crystal structural studies of toxaphene congeners. Quantum chemical calculations for preferred conformers of 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene and their DFT/GIAO C chemical shifts

The ¹H and ¹³C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachloro- (1), 2-exo,3-endo,5-exo,9,9,10,10-heptachloro- (2), 2-exo,3-endo,6-exo,8,9,10,10-heptachloro- (3), 2-exo,3-endo,5-exo,6-endo,8,9,10-heptachloro- (4), 2-exo,3-endo,5-exo,6-endo,8,9,9,10-octachlorobornane (5) and 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene (6) are reported. Their chemical shift assignments have been obtained by means of Pulsed Field Gradient (PFG) Double Quantum Filtered (DQF) ¹H,¹H correlation spectroscopy (COSY), PFG ¹H,¹³C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG ¹H,¹³C Heteronuclear Multiple Bond Correlation (HMBC) experiments. A single crystal X-ray structural analysis was made for compounds 1, 3, 4 and 6. The prevalences of two octachlorobornene rotamers (6a,6b) were elucidated by ab initio MO method and single point DFT/GIAO calculations for ¹³C chemical shifts. Theoretical calculations proved that the single crystal structure of 6 corresponds its most stable conformer in solution.     

The viscosity and density of the methanol + n-nonane, ethanol + n-nonane, and ethanol + n-decane systems

This work presents the results obtained in measurements of the kinematic viscosity and density of the methanol-n-nonane, ethanol-n-nonane, and ethanol-n-decane systems at various temperatures and low n-alkane concentrations (within the concentration range of miscibility). The dynamic viscosities of these systems at 298.15 K were calculated according to free volume theory. The results substantiated the existence of an anomaly in the behavior of viscosity of the methanol-n-nonane system (positive Δlnη values) and its absence for the ethanol-n-alkane systems.     

Relativistic electronic structure of the Pb (001) surface

The surface electronic band structure of the Pb (001) was calculated using the self-consistent, first-principles linear-augmented-plane-wave method and the norm-conserving pseudopotentiai method. In the nonrelativistic case, forbidden gaps appear above and below the Fermi levelin the bulk projected band structure of lead. An occupied surface state at the point and two surface states in a wide forbidden gap above E_F are found. A characteristic feature of the electronic structure of the Pb (001) surface is the absence of a surface state within the forbidden S-P gap in the vicinity of the point. The inclusion of scalar-relativistic effects leads to the merger of several S-P gaps into one wide gap extending throughout the entire Brillouin zone. At the same time, the occupied state at point extends to point and its energy decreases by 2 eV. New, relatively weak surface states in the direction and unoccupied states in the vicinity of the point appear. An unoccupied surface state is found at the bottom of the forbidden gap at point . Including the contribution of the spinorbit pseudopotentiai leads to the appearance of two-spin orbit gas; however, the surface level structure is practically unchanged (except for the disappearance of the unoccupied surface state of P_z-symmetry at point ).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 47–53, October, 1991.     

H, C, N NMR, ESI mass spectral and single crystal X-ray structural characterization of three spiro[pyrrolidine-2,3′-oxindoles]

Three spiro[pyrrolidine-2,3′-oxindoles], 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-phenyl-spiro[3H-indole-3,3′-[3H]-pyrrolizine]-2′-carboxylic acid methyl ester (1), 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-phenyl-spiro[3H-indole-3, 3′-[3H]-pyrrolizine] (2) and 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-(4″-chlorophenyl)-spiro[3H-indole-3,3′-[3H]-pyrrolizine] (3) have been synthesized and their ¹H, ¹³C and ¹⁵N spectra assigned. The chemical shift assignments are based on Pulsed Field Gradient (PFG) Double Quantum Filter (DQF) ¹H, ¹H correlation spectroscopy (COSY), PFG ¹H, ¹³C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG ¹H,X (X = ¹³C and ¹⁵N) Heteronuclear Multiple Bond Correlation (HMBC) experiments. The single crystal X-ray structures of 1–3 have been determined. Compounds 1 and 2 crystallized in monoclinic space group C2/c and compound 3 in monoclinic space group P2₁/c, respectively. Also the ESI-TOF MS data of 1–3 are given.     

Calculation of Absorption Intensities of Cr3+ Ion Pair Lines in Ruby

The calculation of relative intensities of the optical absorption lines of the fourth order pair of Cr³⁺ ions in ruby has been performed assuming the electro-dipole character of the transitions.