Chemical-ionization mass spectra of diterpene alkaloids

The chemical-ionization spectra of diterpene alkaloids have been investigated for the first time with the recording of positive and negative ions [Cl(+) and (–)). A comparison has been made of the CI(+) spectra with the EI and SIMS spectra. It has been shown that the nature of the CI(+) and (–) spectra depends greatly on the type and position of substituents in the lycoctonine skeleton.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 114–122, January-February, 1995. Original article submitted October 31, 1994.     

Mass spectrometric study of sophoramine isomers by the direct analysis of daughter ions (DADI)

In a study of the mass spectra of sophoramine, isosophoramine, and neosophoramine by the direct analysis of daughter ions (DADI) it has been established that the ions with m/e 149 and 136 are formed from the molecular ions. Differences have been found in the DADI spectra of the alkaloids studied that are due to features of the three-dimensional structures of their molecules.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 353–355, May–June, 1979.     

Ionization processes accompaning interaction of excited atoms with CH3CN,CH3COOH,and HCOOH molecules

The fragmentation processes of the molecular ions formed as a result of single collisions of metastable and highly excited Rydberg atoms of noble gases with molecules of acetonitrile, formic acid, and acetic acid have been investigated by a mass-spectrometric method. The correlation between the observed Penning-dissociativeionization mass spectra and the degree of overlap of the moelcular orbitals with vacant orbitals of the metastable atoms determined from the available energy spectra of the electrons formed during Penning ionization has been examined. Complex ions appearing during associative ionization have been discovered. The mechanisms for the formation of the observed ions have been discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 1, pp. 39–46, January–February, 1990.     

Photoionization mass spectrometry of aliphatic monoterpene alcohols

Summary 1. The dissociative processes observed in the photoionization of monoterpene alcohols have been investigated. It has been established that the relative intensities of the peaks of the heavy ions, including the molecular ions, are higher on photoionization than on electron impact.2. It has been found that the mass spectra of the isomeric alcohols obtained on photoionization differ from one another to a greater degree than the electronic mass spectra.Agrophysical Scientific-Research Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 723–726, November–December, 1974.     

Fragmentation of some 1,2-epoxyguaianolides

The mass spectra of four guaianolides with epoxy groups of C₁–C₂ have been studied. A mechanism is proposed for the formation of the main ions. The origin of the secondary fragments has been confirmed by measurements of elementary compositions.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 796–800, November–December, 1980.     

Features of the mass spectra of hetisine bases with an OH group at C-14

The EI mass spectra of five hetisine bases with an OH group at C-14 have been investigated. The main directions of fragmentation are initiated by the cleavage of the C-14-C-20 bond. With the aid of measurements of the elementary compositions of the molecular and fragmentary ions and of a comparison of the B/E linked-scanning and metastable defocusing spectra, the mechanism of the formation of the key fragments has been established and alternative methods for the production of certain ions have been revealed.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 82–89, January–February, 1992.     

Mass spectrometic investigation of the structure and formation mechanism of ions in the autoionization of aliphatic alcohols

The structure and formation mechanism of ions in the field ionization of methanol and ethanol have been studied by isotopic labeling with O¹⁸ and deuterium, and mass spectrometric analysis. It is shown that these alcohols give identical mass spectra in the molecular ion region, these consisting of four lines: M+1, M, M–1, and M–2. The M+2 ions have the structure ROH·H⁺ while the M–1 ions are (R–H)·OH⁺. For methanol the M–2 ions have the structure of formaldehyde, and for ethanol they have those of both an aldehyde and a vinyl alcohol. It is also shown that field ionization may be used to study the catalytic oxidation of alcohols over platinum by free oxygen.     

Anion-exchange behaviour of a number of metal ions on DEAE-cellulose in hydrobromic and hydriodic acid media

Summary The adsorption behaviour of 48 metal ions on DEAE-cellulose layers has been investigated in aqueous hydrobromic and hydriodic acid media. R_F values are given as a function of the hydrobromic and hydriodic acid concentration over the ranges 0.01–6 mol dm^–3 and 0.01–3 mol dm^–3, respectively, and are compared with those obtained with Avicel SF. R_F spectra are comparatively simple in both media, reflecting the strong affinity of the bromide and iodide ions to the DEAE-cellulose phase. Pd, Pt, Re, Au and Hg are distributed chromatographically in either system, while most other metal ions exhibit rather extreme R_F values of near unity or zero. Therefore, the selectivity of the systems is particularly high for Pd, Pt, Re, Au and Hg, providing the possibility of their excellent selective separations.     

Field desorption mass spectra of flavonoid acylglycosides. I. Natural acetyl derivatives

The field desorption mass spectra (FD spectra) of 17 natural flavonoid acetylglycosides have been studied. In the spectra of each of the 0-monoglycosides the molecular ion (M or M + H) appears as the main peak and it is accompanied by the ions of the aglycone (A or A + H) and of the acylated anhydrosugar (S). The intensity of the latter peak is largely connected with the structure of the substance. In the FD spectra of flavone 0-biosides, fragment S is absent but its mass can be calculated from the difference (M – A). Useful information for establishing the position of the acetyl group is given by the fragments S₁ and (M – S₁) corresponding to the detachment of the terminal sugar residue. The FD spectra of flavone C-glycosides differ greatly from the spectra of the 0-glycosides: In them the main peak is that of the ion (M), but peaks (A) and (S) are absent and the ions present resemble the fragmentation of the C-glycosides under the action of electron impact.All-Union Scientific-Institute of Medicinal Plants, Moscow. L. Ya. Karpov Scientific-Research Institute of Physical Chemistry, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 573–582, September–October, 1984.     

Porphyrins

The low and high-resolution mass spectra and the spectra of the metastable ions (DADI) of a number of porphyrins and their copper complexes with –CR=N–R, –CH₂NHR, and –CH₂NRR substituents in the meso position of the porphyrin ring were investigated. The principal pathways of fragmentation of the meso-substituted porphyrins were established.See [1] for communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 773–779, June, 1978.     

Secondary-emission mass spectrometry of hederagenin glycosides and medicagenic acid glycosides

The secondary emission (SE) spectra of six glycosides of medicagenic acid (MA) and of hederagenin have been studied. The (M + H)⁺ ions were observed in the secondary ion spectra (LSIMS) of mono- and biosides of MA and also of a triand a tetraoside of hederagenin in a glycerol matrix. The (M + Na)⁺ ions were recorded in the spectra of tri- and tetraosides of MA. In the majority of cases processes involving the successive splitting out of the carbohydrate units were revealed. Positive- and negative-ion spectra have been obtained on the ionization by bombardment with fast atoms — FAB + and FAB – — of a trioside and a tetraoside of MA. The FAB – spectra are the most characteristic: They show intense peaks of the (M - H)^– ions and of the products of the sequential elimination of the sugar residues.Institute of the Chemistry of Plant Substances, Uzbekstan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 98–102, January–February, 1992.     

Resonant electron trapping and photoelectron spectroscopy for substituted fluorinated nitrobenzenes

Mass spectra have been recorded for dissociative electron capture DEC negative ions together with photoelectron spectra for the molecules of fluorinated nitrobenzenes. Nitrobenzene DEC is governed in the main by orbitals having appreciable contributions from the nitro group atoms. Resonant states are formed in the molecular negative fluoronitrobenzene ions via the Feshbach electronically excited resonance mechanism, which involves the excitation of an electron from a series of filled MO to several vacant MO.Chemical Institute, Bashkir Scientific Center, Urals Branch, Russian Academy of Sciences, Ufa. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 683–688, November–December, 1991. Original article submitted November 27, 1989.     

Mass spectra of alliosterol and its dehydration product and of allosides A and B

The EI and LSIMS mass spectra of alliosterol and its dehydration product and of allosides A and B have been studied. The spectra of alliosterol show features characteristic for sterols of the cholestane series. A comparison of the B/E spectra of some fragments of the ions from alliosterol and its dehydro product has shown the unimportance of the conversion of the former into the latter under mass-spectrometric conditions.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 344–349, May–August, 1992.     

EPR and IR spectral investigations on some leafy vegetables of Indian origin

EPR spectral investigations have been carried out on four edible leafy vegetables of India, which are used as dietary component in day to day life. In Rumex vesicarius leaf sample, EPR spectral investigations at different temperatures indicate the presence of anti-ferromagnetically coupled Mn(IV)–Mn(IV) complexes. EPR spectra of Trigonella foenum graecum show the presence of Mn ions in multivalent state and Fe³⁺ ions in rhombic symmetry. EPR spectra of Basella rubra indicate the presence of Mn(IV)–O–Mn(IV) type complexes. The EPR spectra of Basella rubra have been studied at different temperatures. It is found that the spin population for the resonance signal at g = 2.06 obeys the Boltzmann distribution law. The EPR spectra of Moringa oliefera leaves show the presence of Mn²⁺ ions. Radiation induced changes in free radical of this sample have also been studied. The FT-IR spectra of Basella rubra and Moringa oliefera leaves show the evidences for the protein matrix bands and those corresponding to carboxylic CO bonds.     

Über dieIR-Spektren der dinegativen Ionen einiger polycyclischer Mononitrile und Elektronenübergänge zwischen dinegativen Ionen und neutralen Molekülen

Zusammenfassung Die Nitrilgruppe in den dinegativen Ionen (DA) des mit metall. K in Tetrahydrofuran (THF) erhaltenen 1-Cyanpyrens, 9-Cyananthracens, 4-Cyanbiphenyls und 1- und 2-Cyannaphthalins zeigt sehr breite (50–70 cm^–1) und intensive Bandenv _CN zwischen 2020–2070 cm^–1.DieIR-Spektren im Bereich 2000–2250 cm^–1 wurden zur Untersuchung der Elektronenübergänge zwischenDA und einigen neutralen Molekülen herangezogen.

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IR spectra of some dinegative polycyclic mononitrile ions, and electron transitions between the ions and neutral molecules

The CN group in the dinegative ions of 1-pyrenecarbonitrile, 9-anthracenecarbonitrile, 4-biphenylcarbonitrile, 1- and 2-naphthalenecarbonitriles, resp., obtained with K in tetrahydrofuran (THF), gave rise to very broad (50–70 cm^–1) and intensive bands in the 2020–2070 cm^–1 region.IR spectra in the 2000–2250 cm^–1 region have been used to study the electronic transitions between dinegative ions and some neutral molecules.

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Mit 3 Abbildungen     

Molecular modeling of the influence of complex formation on the conformation and electronic absorption spectra of crown-containing styryl dyes

The conformation and electronic absorption spectra of crown-containing styryl dyes and their complexes with metal salts have been calculated. The long-wave absorption bands have been assigned. It was shown that the observed large hypsochromic shift of the absorption spectra during the formation of complexes of the cis-form of the dyes under consideration with alkaline earth ions is due to a change in the conformation of the chromophore and the resultant approximate prohibition with respect to symmetry of the long-wave electronic transition.Institute of Chemical Physics, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 39–45, March–April, 1993.     

Quantitative analysis of unlabelled and polydeuterated compounds by gas chromatography-mass spectrometry

Summary A system for computer evaluation of gas chromatographic-mass spectrometric analyses of unlabelled and polydeuterated compounds is described. The system has been in routine use for two years and has been found to fulfil most of the needs of the laboratory in connection with studies of steroid and bile acid metabolism. Complete or partial spectra are taken by repetitive magnetic scanning and are recorded on magnetic tape. Methods for qualitative evaluation have been described previously [6, 9]. Quantitative determinations of unlabelled compounds are based on areas of gas chromatographic peaks in selected specific fragment ion current chromatograms generated by the computer. Percentage distribution of molecular or fragment ion species containing 0–19 deuterium atoms is calculated from averaged spectra by comparison with spectra of the unlabelled reference compound analyzed on the same day. When small amounts of material are available and when ions occur in low abundance, repetitive accelerating voltage scanning over a short mass range is used. A slow scan rate, 1–5 s, and a high data sampling rate, 10 kHz, permit a 100–300 fold increase of amplification. After bunching of intensity readings, partial mass spectra are constructed which are treated in the same way as complete spectra.     

ESR,spectroscopic, and quantum-chemical studies on the electronic structures of complexes formed by Cu(I) with radicals

The optical and ESR spectra have been examined for complexes of Cu(I) with various radicals, which contain various numbers of Cl ions in the central-atom coordination sphere. The spin-Kamiltonian parameters have been determined for all these radical complexes, and the observed ESR spectra have been compared with those calculated with allowance for second-order effects. The observed values for the isotropic and anisotropic components of the HFI constant from the central ion have been used to estimate the contributions from the 4s and 3d² _z orbitals of the copper ion to the unpaired-electron MO. Quantum-chemical calculations have been performed by the INDO method on the electronic structures and geometries of complexes formed by CH₂OH with Cu(I) for various Cl contents in the coordination sphere. The radical is coordinated by the orbital on the carbon atom, and the stabilities of the radical complexes decrease as the number of Cl ions in the coordination sphere increases. A geometry close to planar is proposed for the CuCl₄ ^–3 fragment in a complex containing four Cl ions.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 1, pp. 32–38, January–February, 1986.     

Fragmentation of sesquiterpene lactones related to leucomisin

The mass spectra of seven sesquiterpene lactones — leucomisin, austricin, parishin B, parishin C, matricarin, artelin, and artelin diacetate — have been studied. It has been shown that the presence of the conjugated bonds C(1)=C(10), C(2)=0, and C(3)=C(4), and also C(5)=C(6), stabilizes M⁺, and the main fragmentation process is that of the splitting out of the lactone ring. The presence of hydroxy substituents at C(3) and C(8) of the guaiane system does not change the stability of M⁺ under electron impact. The directions of fragmentation have been confirmed by an analysis of spectra obtained by the metastable defocussing of daughter ions and by measuring the accurate masses of the main peaks of the fragmentary ions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 96–101, January–February, 1987.