Chemical ionization over a wide range of pressures. 1. Mass spectra of dimethyl esters of maleic and fumaric acids

Conclusions By using chemical ionization over a wide range of pressures, from 0.01 torr to atmospheric pressure, and also by selecting the reagent gas, different mass spectra of isomers can be obtained, which are suitable for their reliable identification.Under ionization conditions at atmospheric pressure in helium (reagent ions [H(H₂O)_n]⁺), peaks of cluster ions [MGH]⁺ and [2M+1]⁺ are observed in the spectrum of dimethyl fumarate, which are absent in the case of the cis-isomer.Under the conditions of chemical ionization at a normal pressure (0.4-0.2 torr) of the reagent gases Me₃CH, n-C₇H₁₆ and at an ionic source temperature of 50°C, a stereospecific fragmentation of dimethyl maleate [MH]⁺-MeOH is observed, which is absent in the case of the the trans-isomer.In the chemical ionization spectra at reduced pressure of the reagent gases MeOH, EtOH, i-PrOH (0.01 torr), a peak of the cluster ion [MGH]⁺ is observed for dimethyl fumarate, which is absent in the spectra of the cis-isomer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 815–819, April, 1985.     

S1←S0 vibronic spectra and the vapor-state molecular structure of propanal and 2-methylpropanal

The vapor-state absorption spectra have been recorded for propanal PA and 2-methylpropanal MP with path lengths up to 120 m. The initial points in the S₁S₀ electronic transitions have been identified together with various fundamental vibrational frequencies of the PA and MP conformers. They contain nonplanar aldehyde groups in the S₁ states with inversion potential barriers of about 600 cm^–1. The parameters of the internal-rotation potential functions in the S₁ states have been determined, and the corresponding potential functions in the S₀ states have been refined.Chemical Faculty, Lomonosov Moscow University. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 20–25, January–February, 1993.     

Secondary-ion mass spectra of pennogenin glycosides

LSIMS mass spectra of pennogenin glycosides have been studied; the most characteristic ions are (M+H–H₂O)⁺ (with glycerol as the liquid matrix) and (M+Na)⁺ (with glycerol +NaCl as matrix). In both cases the peaks of ions formed as the result of the successive elimination of the carbohydrate units, the breakdown of the bonds of the terminal pyranoses, the cleavage of the bonds of the rings D and E, and the peaks of the ions Agl⁺ and (Agl–H₂O)⁺ were observed.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. All-Union Scientific-Research Institute for Agricultural Biotechnology, All-Union Academy of Agricultural Sciences, Moscow. Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 523–525, July–August, 1991.     

Features of the splitting out of a methyl radical from lycoctonine alkaloids under electron impact

The mass spectra of 53 alkaloids and their derivatives are considered. It is known that the presence of a C₆(OCH₃)-C₇(OH)-C₈ (OH) grouping in C₁₉-diterpene alkaloids leads to a high intensity of the (M - 15)⁺ ions at the expense of the C₆(OCH₃) group and considerably suppresses the competing processes of forming the [M - OH (OCH₃)]⁺ ions in the alkaloids and the (M - 56)⁺ ions in the anhydroxy bases. When the above-mentioned grouping is absent, the (M - 15)⁺ ions are formed mainly by the splitting out of a H₃ from a N-ethyl group.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii. No. 4, pp. 525–536, July–August, 1985.     

Transformations of a polynuclear silver(I) complex with a ligand containing phosphorus and sulfur under the influence of a strong electric field and fast-atom bombardment

Gas-phase transformations of a new polynuclear silver(I) complex Ag3 (L-H)₂NO₃ (where L is Ph₂P(S)CH₂P(S)Ph₂) under the influence of a strong electric field and fast-atom bombardment have been studied using FD and FAB mass spectrometry. Fragmentation of the complex in both cases was shown to proceed in the same way. Differences in the FD and FAB mass spectra of this complex were due to secondary hydrolytic and redox reactions of the ligand.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 1, pp. 50–54, January–February, 1994.     

Voltamperometric determination of uranium and plutonium in alkaline solutions

The simultaneous determination of U(VI), Pu(VI), Pu(V) in 0.5–4.0 M NaOH has been elaborated by means of classical and differential pulse voltamperometry. U(VI) is determined with a dropping mercury electrode (DME) at the half-wave potential of E_1/2=–0.89 V vs. Ag/AgCl reference electrode due to reduction to U(V). The limiting current or peak heights are proportional to uranium(VI) concentration in the range of 1.3.10^–7–3·10^–4 M U(VI). Deviation from proportionality is observed for higher concentrations due to polymerization of uranates. Pu(VI) and Pu(V) are determined with a platinum rotating electrode at E_1/2=–0.02 V due to the reaction Pu(VI)+e^–»Pu(V) and with DME at E_1/2=–1.1 V due to the reduction to Pu(III). The limiting currents of both Pu(VI) and Pu(V) are proportional to their concentrations in the range of 4·10^–6–1.2·10^–3 M Pu. The determination of U(VI), Pu(VI), Pu(V) is not interfered by the presence of the following salts: 2M NaNO₃, 2M NaNO₂, 1.5M NaAlO₂, 0.5M NaF and ions of Mo(VI), W(VI), V(V), Cu(II). The presence of CrO ₄ ^2– and FeO ₂ ^– ions disturbs the determination of U(VI) in 1–4M NaOH, however, contribution of the reaction Fe(III)+e^–»Fe(II) to uranium reduction peak can be calculated from the height of the second peak Fe(II)+2 e^–»Fe(0).     

Investigation of the surface of Ni-Pd catalysts by IR spectroscopy

The reaction of carbon monoxide with the surface of Ni, Pd, and Ni-Pd catalysts, deposited on -Al₂O₃, was investigated at 25°C by IR spectroscopy in conjunction with an adsorption volumetric technique. The IR spectra contained the following absorption bands (v, cm^–1): 2020–2100 (AB1) (linear and subcarbonyl forms of adsorbed CO); 1945–1985 (AB2) (bridging); 1920–1940 (AB3) with a shoulder at 1870–1885 (AB4) (bridging and many-center). In the spectrum of Ni the absorption band AB5 appears at 1770–1780 (CO-Ni⁺). It appears with surface coverage a 1.3 mole CO/mole M. The optical density (A) of AB1 for Ni₉₇Pd₃ is appreciably higher than for the other investigated samples. In the Ni-Pd catalysts the intensity of AB2 in relation to AB1 is higher than in nickel. The introduction of K⁺ ions into the support of the bimetallic sample reduces the optical density of AB1. In modified Ni-Pd-K the AB3 and AB4 bands disappear.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1276–1282, June, 1992.     

Nucleophilic substitution in dibenz[b,d]iodolium and 11,12-dihydro-10H-dibenz[b,g]iodocinium cations

Treatment of dibenz[b,d]iodolium tetrafluoroborate with NO₂ ^–, Br^–, and N₃ ^– ions gave, along with nucleophilic substitution products, 2-nitro-, 2-bromo-, and 2-azido-2-iodiphenyls, diphenyl, 2-iododiphenyl, and 2,2-diiododiphenyl (products of one electron reduction), whereas 11,12-dihydro-10H-dibenz[b,g]iodocinium tetrafluoroborate underwent nucleophilic substitution with all three nucleophiles to give a single product in each case: 1-(2-nitrophenyl)-, 1-(2-bromophenyl)-, or 1-(2-azidophenyl)-3-(2-iodophenyl)propane.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 405–412, March, 1998.     

Mass-spectrometric study of physiologically active β-thiosemicarbazones of N-alkylisatins

The molecular ions of isatin (I) and N-methyl- (II) and N-ethylisatin (III) -thiosemicarbazones undergo fragmentation via many pathways with the elimination of NH₃, H₂S, CO, CH₂N₂, CHN₃, CH₂N₂S, CH₂NS, and CHNS particles; this is due to primary localization of the charge on the heteroatoms of the thiosemicarbazone residue. A previously unknown rearrangement, which consists in migration of an HS group to the -carhon atom of the heteroring with subsequent ejection of a CHN₃ fragment. The [M — CO]⁺ ions undergo fragmentation with the elimination of CH₂N₂S; in the case of II and III fragmentation is preceded by detachment of a hydrogen atom (II) or a methyl group (III) from the substituent attached to the ring nitrogen atom. The [M — CO, -H, -CH₂NS]⁺ (II) and [M — CO, -CH₃, -CH₂N₂S]⁺ (III) ions undergo fragmentation with the ejection of HCN in two ways through both the ring nitrogen atom and the thiosemicarbazone residue. Schemes for the principal pathways of fragmentation and rearrangements are presented. The compositions of the ions were confirmed by the high-resolution mass spectra and the mass spectra of the N-deuteroalkyl derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 75–79, January, 1979.     

Electrochemical synthesis and magnetic studies of neutral transition metal imidazolates and pyrazolates

Summary The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an Me₂CO solution of the diazole to yield complexes of the general formula: [M(Iz)₂] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)₂] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(PrⁱIz)₂] (where M = Co, Ni, Cu, Zn; PrⁱIz = 2-isopropylimidazolate); [M(pyIz)_n] (where M = Co^III, Cu^II, Zn^II; pyIz = 2-(2-pyridyl)imidazolate); [M(Pz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; Pz = pyrazolate); [M(ClPz)_n] and [M(IPz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; ClPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me₂Pz)_n] (where M = Co^II, Cu^I, Zn^II; Me₂Pz = 3,5-dimethylpyrazolate) and [M(BrMe₂Pz)_n] (where M = Co^II, Ni^II, Cu^I, Zn^II; BrMe₂Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S= ) model for an infinite one-dimensional linear chain, yielding best fit values of J=–62––65cm^–1 andg = 2.02–2.18. Data for the cobalt complexes were fitted to an Ising (S= ) model with J=–4.62––11.7cm^–1 andg = 2.06–2.49.     

6-Chloroapigenin fromEquisetum arvense L.

A new compound 6-chloroapigenin, C₁₅H₉C10₅, M⁺ 304, mp 305–306°C, _max 274, 336 (methanol) has been isolated from the ether-soluble fraction of a methanolic extract of the field horsetail. On the basis of the results of UV and PMR spectroscopy and mass spectrometry, the structure of 6-chloro-4,5,7-trihydroxyflavone has been established for this compound.Irkutsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR, All-Union Scientific-Research Institute of Medicinal Plants, Moscow. I. M. Sechenov First Moscow Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 499–501, July–August, 1980.     

Secondary-ion mass spectrometry of lycotetraosides of the spirostan and furostan series

The secondary-ion mass spectra of seven steroid lycotetraosides have been obtained by the SIMS method. On the use of a glycerol matrix, all the compounds of the spirostan series, including those with an additional carbohydrate substituent a C-24, formed the (M+H)⁺ ions, while a lycotetraoside of the furostan series formed the (M–H₂O+H)⁺ ion. They subsequently decomposed by the alternative successive elimination of the terminal carbohydrate units of the lycotetraose. Substituents at C-25 and C-26 were ejected in the form of glucose molecules. Fragments of the aglycon and of the lycotetraoside moieties of the molecules were recorded. When NaCl was added to the same matrix, all the compounds gave preferentially the (M+Na)⁺ and (M+2Na–H)⁺ ions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. All-Union Scientific-Research Institute of Agricultural Biotechnology, Lenin All-Union Academy of Agricultural Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 53–58, January–February, 1991.     

Vibronic spectra and S1 excited electronic state molecular structures for acetyl chloride and acetyl fluoride

Vapor-state absorption spectra have been recorded for acetyl fluoride and acetyl chloride and also for deuterated derivatives with path lengths up to 40 m. The origins of the S₁S₀ transitions have been derived, together with the torsional-vibration energy levels in the ground state S₀ and excited singlet state S₁. Fitting the calculated and observed rotational contours of the vibronic bands has been used to estimate the geometrical parameters in the S₁ states. The carbonyl groups in the S₁ states are nonplanar. The internal-rotation potentials have been determined for acetyl fluoride and acetyl chloride in the S₁ and S₀ states. The relative intensities of the torsional transitions in those states indicate that the minima in the potential energy are appreciably displaced along the torsional coordinate in the S₀ and S₁ states.Chemical Faculty, Lomonosov Moscow University. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 26–30, January–February, 1993.     

A mass-spectroscopic study of the terpenoid coumarins mogoltadone,gummosin, and farnesiferol A

Summary The mass spectra of the terpenoid coumarins mogoltadone (I), gummosin (II), and farnesiferol A (III) and their deuterium analogs (IV–VI) have been studied. It has been shown that the main and auxiliary directions of the decomposition of the molecular ions of the substances are similar to the dissociative ionization of the terpenoid coumarins studied previously. The fragmentation of the ions corresponding to the terpene residues of these compounds permits the determination of the presence of keto and hydroxy groups in the bicyclic terpene system and provides the possibility of distinguishing the stereoisomers (II) and (III) with different orientations of the hydroxy groups and also of determining the presence in the terpene residue of a gem-dimethyl grouping in the vicinal position to the keto or hydroxy group.M. V. Lomonosov Moscow State University. Patrice Lumumba International Friendship University. Moscow Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 207–212, March–April, 1977.     

Field-desorption mass spectra of flavonoid acylglycosides. II. Natural cinnamoyl and benzoyl derivatives

The field-desorption mass spectra of 14 flavonoid glycosides esterified with p-coumaric, ferulic, caffeic, p-hydroxybenzoic, and gallic acids have been studied. For all the compounds the molecular ions and the ions of the aglycone (A) were obtained as the main peaks. The spectra also contained a number of other fragmentary ions, including the ion of the acylated anhydrosugar. For flavonol glycosides in which the carbohydrate is esterified by cinnamic acids, the (A + Ac), and for the diacylglycosides the (A + 2 Ac), ions are diagnostic. The formation of these strong ions corresponding in mass to the molecules of the mono- and diacylated aglycone permits the assumption of the existence of acyl migration in the breakdown of the initial molecular ion.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. L. Ya. Karpov Scientific-Research Institute of Physical Chemistry. Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 582–589, September–October, 1984.     

Acidity function scale for H2SO4 solutions in phenol-acetone solvents with low water content at 25°C

The indicator method was employed to measure the acidity function H ₀ ^S of H₂SO₄ solutions in solvents consisting of an equimolar mixture of phenol and acetone with 0.8% water (from 3.6·10^–4 to 2.6·10^–2 M H₂SO₄) and 2.5% water (from 4.3·10^–4 to 0.32 M H₂SO₄) and of phenol and acetone in a molar ratio of 1:1.5 with 0.67% water (from 1.63·10^–4 to 7.77·10^–2 M H₂SO₄) and 2.09% water (from 4.49·10^–4 to 0.35 M H₂SO₄) at 25°C. The indicators employed were 4- and 2-nitroaniline.Deceased.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Lenneftekhim Scientific-Commercial Association, St. Petersburg. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 72–78, January, 1992.     

Mass-spectrometric study of 2- and 4-azafluorenones

A mass-spectrometric study of 2- and 4-azafluorenones and their mono- and polymethyl derivatives showed that the presence of a methyl group in the benzene ring leads to a sharp increase in the relative intensity of the [M — H]⁺ ion peak. In contrast to the fragmentation of 2- and 4-azafluorenes, the mass spectra of monomethyl-substituted compounds do not contain an [M — CH₃]⁺ fragment; this is probably associated with expansion of the pyridine or benzene ring to a seven-membered ring in the step involving the formation of the molecular ion due to inclusion of the methyl group. The intensity of the [M — CO]⁺ ion peak in the mass spectra of the 4-azafluorenones is higher by a factor of two with respect to the 2-azafluorenone isomers, and the [M — HCN]⁺ and [M — H, -HCN]⁺ ion peaks observed in the mass spectra of 2-azafluorenones are absent in them.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 89–95, January, 1979.     

An ab initio study of electronic spectra and excited-state properties of 7-azaindole in vapour phase and aqueous solution

The geometries of 7-azaindole (7AI), its tautomer (7AT), and 7AI–H₂O and 7AT–H₂O complexes were optimised in the ground state and some low-lying singlet excited states using the 3-21G basis set. Differences of total energies of the optimised ground and excited states and the vertical excitation energies of these systems were used to explain the observed electronic spectra. Effect of solvation of these systems in bulk water was studied using the polarized continuum model (PCM). The mode of binding of a water molecule in the S₂(n–π^*) excited state of 7AI was found to be quite different from those in its ground and π–π^* excited states. It is shown that crossing of the lowest two singlet excited-state potential surfaces S₁(π–π^*) and S₂(n–π^*) of 7AI occurs in the vapour phase under geometry relaxation while on interaction with water, the S₂(n–π^*) excited state is raised up appreciably going even above the S₃(π–π^*) excited state. Ground- and excited-state molecular electrostatic potential mapping was carried out, which led to valuable information regarding the nature of excited states of the above-mentioned systems.     

Transition metal(II) complexes of (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone

A new organometallic ligand, (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone (HCfmc) and six transition metal(II) complexes thereof M(Cfmc)2·nH2O (M=Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+; n=0–2) have been prepared and characterized by elemetal analyses, i.r., u.v., 1H-n.m.r. spectra, electrochemical properties, fluorescence spectra and molar conductances. The HCfmc ligand acts as a bidentate donor, coordinating to the metal ions via nitrogen and sulfur atoms with a trans-configuration.     

Analytical study of a cadmium ion-selective ceramic membrane electrode

Summary A cadmium ion-selective membrane electrode has been developed by applying a hot-pressing method. The membrane contains cadmium sulphide, silver sulphide, and copper(I)-sulphide.The best response was obtained with a membrane containing less than 30% of copper(I) sulphide and more than 5% of cadmium sulphide. The Nernstian slope was secured over an activity range of 10^–1 to 10^–6 M, and potentiometric analysis could be carried out over a concentration range of 10^–1-10^–7 M. The potentials were maintained at constant values over more than 6 months. Also, the potentials satisfied the Nernst's factor 2.303 RT/2F at the temperature range between 0 and 95°C. Among the common ions, silver, copper(II), iron(III), mercury(II), sulphide, and iodide ions interfered seriously. However, about 10–100 times of lead and bromide ions and more than 1000 times of alkali metal, alkaline earth metal, zinc, aluminium, nickel, cobalt, manganese(II), perchlorate, and nitrate ions did not interfere at all.

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Analytische Untersuchung einer cadmiumionenselektiven keramischen Membranelektrode

Zusammenfassung Die Membran wurde durch Pressen von Cd-, Ag und Cu(I)-sulfid bei 200–500°C und 3–7 t/cm² hergestellt. Die beste Ansprechempfindlichkeit ergab sich bei einem Gehalt von <30% Cu₂S und >5% CdS. Die Nernstsche Gleichung war gültig im Bereich von 10^–1–10^–6 M, der analytische Bereich war 10^–1–10^–7 M. Die Potentiale konnten mehr als 6 Monate auf einem konstanten Wert gehalten werden. Sie entsprachen dem Nernstschen Faktor, 2,303·R·T/2 F, im Temperaturbereich von 0–95°C. Erhebliche Störungen werden durch Ag⁺-, Cu²⁺-, Fe³⁺-, Hg²⁺-, S^2– und J^–-Ionen verursacht. Jedoch verursachen etwa 10–100fache Mengen von Pb²⁺- und Br^–-Ionen sowie mehr als 1000fache Mengen von Alkali-, Erdalkali-, Zn²⁺-, Al³⁺-, Ni²⁺-, Co²⁺-, Mn²⁺-, ClO₄ ^–- und NO₃ ^–-Ionen keine Störungen.

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The authors thank Dr. S. Kisaka, Dr. K. Sugihara, Dr. S. Hayakawa and Dr. S. Mori for their encouragement in this work.