Protonation of amino and hydroxypyrimidines. NMR-spectra and structures of mono and dications

Proton-NMR. spectra of amino- and hydroxypyrimidines including biologically important bases have been measured in four solvents: CF₃COOH, CF₃COOH? SO₂, FSO₃H and FSO₃H? SbF₅–SO₂ at 27° and ?55°C. In CF₃COOH mono-cations are formed, whereas in FSO₃H and FSO₃H? SbF₅–SO₂ double protonation occurs. In each case the structures of the protonated species are derived from the chemical shifts of CH, NH and OH protons and proton-proton spin coupling constants. A combination of the measurements described leads to a complete assignment of all proton resonances of the protonated pyrimidines. This approach is also recommended for the structural determination of heterocyclic compounds.     

The chemical transport of molybdenum and tungsten and of their dioxides and sulfides

Experiments have been made and an extensive thermodynamic discussion has taken place concerning the chemical transport of Mo, W, MoO₂, WO₂, MoS₂ and WS₂ in the presence of iodine. Efforts have been made to find the species via which Mo and W can migrate within the gas phase.Results: In each case the transport proceeds via the oxide iodides MoO₂J₂ and WO₂J₂ respectively, as already known for the dioxides. Thus the chemical transport of Mo, W, MoS₂ and WS₂ needs not only J₂ but also H₂O, usually liberated from the wall of the quartz ampoule.By means of J₂ + H₂O, the metals can be transported into the high temperature region of the ampoule (e.g., 1050 → 1150°C), whereas the transport of the sulfides proceeds in the opposite direction (e.g., 900 → 700°C).For the sulfide-transport the influence of the ratio of the transport agents $\text{J}{}_2\text{H}{}_2\text{O}$ has been discussed.The water content of the quartz glass out of which the ampoules are made is an important source for water, influencing the reactions.The addition of graphite which considerably lowers the H₂O partial pressure prevents any transport of the metals or the sulfides, which proves that the use of J₂ alone as a transport agent is insufficient in these cases.The gaseous iodides MoJ_x and WJ_z are without any importance under the experimental conditions used for the transport of the metals, their dioxides and sulfides.The partial pressures of MoO₂(OH)₂ and WO₂(OH)₂ under the experimental conditions chosen may usually be neglected. But in the system $\text{MoO}{}_2\text{H}{}_2\text{O}$ the transport via MoO₂(OH)₂ (1000 → 800°C) has been observed.The synthesis of MoO₂ and WO₂, starting with the elements or with powder of metal and trioxide is promoted by the addition of J₂. The reaction steps involved are discussed.     

Synthesis and characterization of polymers and copolymers of vinylruthenocene

Homopolymers of vinylruthenocene and its copolymers with methyl acrylate, styrene, and n-vinylpyrrolidinone have been prepared by free-radical polymerization. No evidence for the electron transfer termination mechanism postulated for polymerization of vinylferrocene was observed. Yields of soluble polymers were 40–90% with M _w (4–25) × 10³ and M _w/M _n = 3.0–13.2. TGA analysis showed little weight loss up to 300°C but rapid decomposition above 300°C. Polyvinylruthenocene is a highly brittle material with T_g above 250°C. Torsional braid analysis of the copolymer samples showed T_g in the range 90–130°C which in some samples increased upon cooling and reheating. Several samples showed weak thermal transitions occurring prior to or following T_g. The rise in T_g upon cooling and reheating is indicative of possible decomposition, crosslinking, or realignment of the polymer chains.     

Mass and NMR spectra of haplophyllidine and perforine and of their derivatives

Conclusions The mass and NMR spectra of haplophyllidine, perforine, and their derivatives have been studied. The influence of the open and cyclic forms of the molecular ion on the nature of the fragmentation has been discussed. The main routes of fragmentation of the compounds considered are due to the presence of substituents at C₈ and C₄.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 4, pp. 273–279, 1969     

Synthesis and structures of organoantimony and organobismuth derivatives of 4-sulfophenol and 2,4-disulfophenol

Tetraphenylbismuth 4-hydroxybenzenesulfonate (I) and tetraphenylantimony 4-hydroxybenzenesulfonate (II) are synthesized in yields up to 80% by the reaction of pentaphenylbismuth and pentaphenylantimony, respectively, with 4-sulfophenol. Compounds I and II are also prepared by the ligand redistribution reaction from pentaphenyl compounds of bismuth and antimony and triphenylbismuth bis(4-hydroxybenzenesulfonate) and triphenylantimony bis(4-hydroxybenzenesulfonate), respectively, in yields up to 87%. The recrystallization of compounds I and II from water gives crystalline hydrates Ph₄BiOSO₂C₆H₄(OH-4) · H₂O (III) and Ph₄SbOSO₂C₆H₄(OH-4) · H₂O (IV). Pentaphenylbismuth and pentaphenylantimony react with 2,4-disulfophenol in acetone, regardless of the ratio of the starting reactants, to form bis(tetraphenylbismuth) 4-hydroxybenzene-1,3-disulfonate (V) and bis(tetraphenylantimony) 4-hydroxybenzene-1,3-disulfonate (VI) in yields up to 74%. According to X-ray diffraction data, coordination of the bismuth atoms in compound I is trigonal-bipyramidal with the axial oxygen atom of the 4-hydroxybenzenesulfonate group (Bi···O 2.764 Å). In compound II, coordination of the Sb atom is tetrahedral (CSbC angles 106.2°–112.3°). In crystal III, the distances between the central atom and the nearest oxygen atoms of the arenesulfonate group and the hydrate water molecule are 3.094 and 3.125 Å, respectively. Crystals V and VI consist of doubly charged anions of 2,4-disulfophenol and several distorted tetrahedral cations of tetraphenylbismuthonium (CBi(1)C, CBi(2)C angles and Bi(1)-C, Bi(2)-C bond lengths vary in the intervals 102.1°–122.7°, 105.4°–114.0° and 2.103–2.230, 2.187–2.209 Å, respectively) and tetraphenylantimonium (CSb(1)C, CSb(2)C angles and Sb(1)-C, Sb(2)-C bond lengths 106.3°–112.2°, 101.3°–122.4° and 2.095–2.110, 2.092–2.123 Å, respectively). The Bi(1) and Sb(2) atoms are coordinated by one of the oxygen atoms of the 2,4-disulfophenol anions (distances Bi(1)···O(3) 2.803, Sb(2)···O(1), 2.704 Å).     

Synthesis and properties of polymethylgermanosilanes and polymethylgermanocarbosilanes

A series of polygermanosilanes and polygermanocarbosilanes with methyl, hydride, and vinyl substituents was synthesized by the Wurtz-Kipping reaction through dechlorination of mixtures of R¹R²SiCl₂ or R¹R²SiClCH₂Cl (R¹ and R² = H, Me, vinyl) and Me₂GeCl₂ in the presence of ultrafine suspension of sodium in toluene. The effect of the nature of substituents in the initial monomers on the yield, composition, and structure of the final products was studied by means of X-ray fluorescence analysis; FTIR spectroscopy; and ¹H, ¹³C, and ²⁹Si NMR spectroscopy. By means of size-exclusion chromatography, it was shown that methyl-and hydride-containing polymers have a unimodal molecular mass distribution (the polydispersity index does not exceed 4). The use of vinyl-substituted monomers results in an increase in polydispersity (the polydispersity index becomes approximately 20). At the same time, the yield of inorganic residue during pyrolysis in an inert atmosphere at 1100°C increases from 20 to 40% according to dynamic TGA data.     

On the synthesis and polymerization of t-butyl-p-vinylperbenzoate and the grafting of its homo- and copolymers

The monomer initiator t-butyl-p-vinylperbenzoate (TBVP) was synthesized and its homo- and copolymerization with styrene, methacrylonitrile, isoprene and phenylmethacrylate was investigated. TBVP is preponderantly incorporated in all four systems; values of Q = 2.27 and e = ?0.13 characterize TBVP as a weak donor with a high monomer reactivity. Kinetic considerations show that all propagation steps in which TBVP takes part are faster or at least as fast as the self-propagation steps of the comonomers used. Rate constants and activation energies of the thermal decomposition of poly(t-butyl-p-vinylperbenzoate) and poly(t-butyl-p-vinylperbenzoate-co-styrene) were determined. The polymer initiators were used for grafting experiments with styrene, acrylonitrile, and methyl methacrylate. The data evaluated for the grafting efficiency, the success of grafting, and the degree of grafting show that these polymers of p-vinylperbenzoate are efficient initiators.     

Quantum-Chemical Analysis of Electronic Excitation and Reactivity of Olefins and Dienes

Results obtained in studying the structure of olefin and diene molecules, and complexes of these, in the ground and lower excited states by RHF, ROHF, GVB/DN, and 6-31G^* quantum-chemical methods are presented. Attention is paid to the identity of the main structural and electronic parameters of triplet T ₁ and singlet S ₁ states forming a reactive fourfold spin-degenerate diradical equilibrium excited state (S·T)₁ having the lowest energy. A new mechanism of cyclodimerization of ethylene and tetrafluoroethylene and anionic polymerization of dienes, involving the (S·T)₁ states, is suggested.     

Quantification of polyphenols and flavonoid content and evaluation of anti-inflammatory and antimicrobial activities of Stenocereus stellatus extracts

The hexanic, ethyl acetate and methanolic extracts from branches of Stenocereus stellatus were tested in both the 12-O-tetradecanoylphorbol-13-acetate (TPA) – induced ear oedema model and antimicrobial activity assay. The % of oedema inhibition, the Minimum Inhibitory Concentration (MIC), as well as the polyphenolic and flavonoid content were determined. Also, extracts were analysed by gas chromatography–mass spectrometry (GC–MS). In TPA model, the three extracts showed moderate oedema inhibition. In the antimicrobial activity assay, methanolic extract shows better MIC against all strains. The lowest MICs were for Candida albicans (31 μg/mL) and Rhizopus sp. (15 μg/mL). Also, 50.78 mg eq. of gallic acid/g extract of polyphenol and 115.12 mg eq. of catequine/g extract of flavonoids content were founded in ethyl acetate extract. In the chromatographic analysis, β-sitosterol, β-amyrine, betulin and some other molecules were identified. The results show that S. stellatus possess antimicrobial activities against some fungus species.     

Preparation and reactions of nitrosyl-tetrazene derivatives of Rh and Ir

Compounds of formula [M(NO)(PPh₃)(N₄R₂)] (I) (M  Rh, Ir; R  SO_2^? C₆H₄CH₃) have been obtained by the interaction of M(NO)(PPh₃)₃ with p-toluene-sulphonyl azide in benzene. These new compounds are formulated as tetrazene derivatives on the basis of chemical and spectroscopic data. They react with ligands, L, (e.g. CO, PPh₃ to give pentacoordinated species of formula [M(NO)(PPh₃(L)(N₄R₂)].The tetrazene derivatives yield the new nitrosyl compounds, M(NO)(PPh₃)Cl₂ (II) on treatment with HCl, the nitrogen-containing residue being converted into RN₃ and RNH₂ species. The compounds (II) are coordinatively unsaturated, and react with ligands L in the same manner as compounds (I), giving new derivatives of formula M(NO)(PPh₃)(L)Cl₂.IR and NMR spectra of the new compounds are reported and discussed. The presence in solution of a structure in which the chelate tetrazene ring has opened {e.g. [M(NO)(PPh₃)(NR)(N₃R)]} is suggested by NMR studies.     

Determination of Mo,W and Zr in molybdates and tungstates of zirconium and titanium

Molybdate and tungstate of zirconium and titanium gels, used as matrices of ⁹⁹Mo/^99mTc and ¹⁸⁸W/¹⁸⁸Re generators, were synthesized under different conditions, in order to establish their performance and to choose the most appropriate gel to produce commercially. This type of generators demands a high content of Mo or W (>25%) in the matrices, since they use ⁹⁹Mo and ¹⁸⁸W of low specific activities. Therefore, it is of vital importance, to know the concentration of W and Mo in these gels, to determine their viability as matrices of the ⁹⁹Mo/^99mTc and ¹⁸⁸W/¹⁸⁸Re generators. There are different analytical methods to determine Mo and W, however, the presence of Zr and Ti in these gels, in many occasions, interfere in the analysis, imposing the previous separation of both metals before their determination. Therefore, the preparation time of the sample, the cost and the generation of chemical waste of these analyses are increasing. In order to eliminate these difficulties, the concentration of Mo, W and Zr of approximately 43 gels of molybdate and tungstate of zirconium and titanium, were evaluated by NAA without preparation of the samples. The results of this study reveal that the conditions of preparation of the gels influence directly their Mo and W content. In general, the titanium molybdate gels possess, on the average, a larger content of Mo (37%) than the zirconium molybdate gels (30%), while the titanium tungstenate gels contain only 8.5%.     

Synthesis and properties of isocyanate and isothiocyanate d1- and d2-complexes of vanadocene

The reactions of vanadocene and its halides Cp₂VCl and Cp₂VCl₂ with R₃MNCX (M  Sn, Si, X  O, S) and R₂M(NCX)₂ in various molar ratios have been studied. The reactions proceed either by an exchange of groups, with no change in the oxidation state of vanadium, or by an oxidative addition of pseudohalide ligand: V^II → V^III; V^III → V^IV. Oxidative addition results in the formation of (R₃M)₂ or gaseous hydrogen (in the reaction with HCl) in the reaction products.We have prepared the first ever monomeric and readily oxidisable d²-complexes of V^III of Cp₂VNCX-type and asymmetric d¹-complexes of Cp₂V(Cl)NCX type, which, although rather stable in air, undergo disproportionation into symmetric d¹-complexes on heating. In transmetallation reactions the ligand activity is found to increase in the order C1 < NCO < NCS. The complexes were characterised by GLC analysis, IR and ESR spectroscopy. A general scheme for the disproportionation reaction of asymmetric complexes of vanadocene is supported by differential thermal analysis data.     

Micro- and semimicrodetermination of carbon and hydrogen

Summary Experiences in the determination of carbon and hydrogen with different methods are dealt with and an apparatus is described which uses a new method for vaporization of the sample, a new tube filling, and modified absorption tubes. Tapered ground joints, flat ground joints, ball and socket ground joints and flexible metal tubes are used to ascertain tightness of the apparatus without introducing risk of breakage. The accuracy for microanalyses with samples between 2 and 5 mg is 0,1% for hydrogen and 0,3% for carbon, for semimicroanalyses with samples between 10 and 20 mg 0,05% for hydrogen and 0,2 for carbon.

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Zusammenfassung Erfahrungen mit verschiedenen Methoden zur Bestimmung von Kohlenstoff und Wasserstoff werden mitgeteilt. Eine neue Apparatur für ein neuartiges Verfahren zur Vergasung der Analysensubstanz mit neuer Rohrfüllung und abgeänderten Absorptionsröhrchen wird beschrieben. Kegel-Flach-und Kugelschliffe sowie biegsame Metallröhren gewährleisten eine gasdichte Apparatur, ohne deren Bruchsicherheit zu mindern. Die Genauigkeit der Resultate bei Mikrobestimmungen mit 2 bis 5 mg Einwaage beträgt 0,1% für Wasserstoff und 0,3% für Kohlenstoff, bei Halbmikroanalysen mit Einwaagen von 10 bis 20 mg 0,05% für Wasserstoff und 0,2% für Kohlenstoff.

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Résumé On met en uvre des expériences pour le dosage du carbone et de l'hydrogène par différentes méthodes et décrit un appareil qui utilise un nouveau procédé de vaporisation de l'échantillon, un nouveau remplissage du tube à combustion et des tubes d'absorption modifiés. On emploie des rodages côniques, plans, sphériques et des tubes de métal flexibles pour assurer l'étanchéité de l'appareil sans introduire de risque de casse. La précision des microanalyses avec des prises d'échantillon allant de 2 à 5 mg est 0,1% pour l'hydrogène et 0,3% pour le carbone; pour les semi-micro analyses, avec des prises allant de 10 à 20 mg, on trouve 0,05% pour l'hydrogène et 0,2% pour le carbone.

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With 4 figures.     

Synthesis and properties of ansa-titano- and ansa-zirconocenes

A series of methyl and allyl derivatives of ansa-titano- and ansa-zirconocenes with isopropylidene or dimethylsilyl bridging groups were synthesized. A dinuclear complex, [Me₂C(C₅H₄)₂]₂Ti₂O₂, resulting from the thermal decomposition of the corresponding dimethyl derivative of ansa-titanocene in the air, was characterized by X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 967–969, May, 1993.     

Synthesis and Structure of YbCuGe and YbIrGe

Summary. The equiatomic ytterbium–transition metal–germanides YbCuGe and YbIrGe were synthesized in single crystalline form from CuGe and IrGe master alloys and ytterbium via the Bridgman technique and they were characterized through their X-ray powder patterns. The structures were refined from X-ray single crystal diffractometer data: NdPtSb type, P6₃mc, a=421.36(8), c=703.9(1) pm, wR2=0.0234, 210 F² values, 11 variable parameters, BASF=0.35(9) for YbCuGe and TiNiSi type, Pnma, a=671.09(6), b=421.55(5), c=757.16(7) pm, wR2=0.0782, 519 F² values, 20 variable parameters for YbIrGe. The copper (iridium) and germanium atoms build up [CuGe] and [IrGe] networks. In YbCuGe the two-dimensional [CuGe] network consists of puckered layers of Cu₃Ge₃ hexagons (247pm Cu–Ge) that are charge balanced and separated by the ytterbium atoms. In contrast, the ordered Ir₃Ge₃ hexagons show a strong orthorhombic distortion and the [IrGe] network is three-dimensional with a distorted tetrahedral germanium coordination around iridium with almost equal Ir–Ge distances (252–259pm). The ytterbium atoms fill cages within this network. The cell volumes of YbCuGe and YbIrGe are indicative for purely trivalent ytterbium.     

Synthesis and properties of a series of porphyrin-nicacid dyads and their Mn and Zn complexes

In this article, a series of porphyrin-nicacid dyads and their Mn and Zn complexes were synthesized and characterized by elemental analysis, UV–Vis, IR, MS, and ¹H NMR spectroscopies. Fluorescence studies show that for increasing length of alkoxy chains the fluorescence intensity and quantum yield of the porphyrin ligands is C₂ > C₃ > C₄ > C₅ > C₆ > C₁₀. Electrochemical results indicate that the length of side chain has little effect on the redox potential.     

Kinetics and mechanism of mercuridestannylation of phenylstannatranes and related derivatives

The kinetics and mechanism of mercuridestannylation of phenylstannatrane derivatives, PhSn(OCH₂CH₂)₃N and PhSn(OC₆H₄)₃N have been investigated relative to model systems PhSnBu₃, PhSn(OMe)₃ in solvent MeOH. For the latter two, the reaction proceeded via the following patternn with k₂ > 10 k′₂

For the stannatranes, step (iii) was not observed. The order of reactivity was shown to be PhSnBu₃ > PhSn(OCH₂CH₂)₃N = PhSn(OC₆H₄)₃ N ⪢ PhSn(OMe)₃.Arguments are made for rate-determining CSn bond fission in reaction (i). Stabilisation of the developing the charge on Sn is important and the enhanced reactivity of the stannatranes is explained by SnN transannular interactions.Values of k₂ and k′₂ were obtained for PhSnBu₃ and PhSn(OMe)₃ which enabled K to be evaluated in each case.     

Synthesis and reactivity of furazanyl- and furoxanyldiazonium salts

Diazotization of aminofurazans (1) and 4-aminofuroxans (2) with nitrosylsulfuric acid in a mixture of conc. H₂SO₄ and H₃PO₄ has been studied and offered as a general method for preparing furazanyl- (3) and furoxanyldiazonium (4) salts. It has been shown that reactions with the retention of the N-N-group (azo coupling, formation of triazenes and azides) are typical of salts3 and4, while elimination of the N₂ molecule (Sandmeyer reaction, hydrolysis, reduction) is not typical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1949–1953, November, 1993.     

Ab initio and DFT investigation of the structures and properties of chloromethyl and chlorofluoromethyl peroxyl radicals

Ab initio and Density Functional Theory (DFT) calculations were performed to determine the equilibrium geometries, charge distributions, spin density distributions, dipole moments, electron affinities (EAs), and C–O bond dissociation energies (BDEs) of CH₂ClO₂^? CHCl₂O₂^?, CCl₃O₂^?, CF₂ClO₂^?, CFCl₂O₂^?, and CHFClO₂^? peroxyl radicals. The C–H BDEs of the parent methanes were calculated using the same levels of theories. Both MP2(full) and B3LYP methods, using the 6‐31G(d,p) basis set, were found to be capable of accurately predicting the geometries of peroxyl radicals. The B3LYP/6‐31G(d,p) method was found to be comparable to high ab initio levels in predicting C–O BDEs of studied peroxyl radicals and C–H BDEs of the parent alkanes. The progressive chlorine substitution of hydrogen atoms in methyl peroxyl radicals results in an increase (decrease) of the spin density on the terminal (inner) oxygen, a decrease in dipole moments, and an increase in electron affinities. The substitution of fluorine by chlorine in the series CF₃O₂^? – CCl₃O₂^? was found to lengthen (destabilize) the C–O bonds. Both C–O BDEs and EAs of peroxyl radicals (RO₂^?) were found to correlate well with Taft σ* substituent constants for the R groups. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005