Studies in the benzodiazine series

The reaction of acetylenedicarboxylic acid and 2,3-diaminoanisole has given two isomeric quinoxalin-2-ones, from which the corresponding 5-and 8-hydroxy derivatives have been obtained. Their structures have been shown by the independent synthesis of one of the isomers. Tetrazolo[4,5-a]- and s-triazolo[4,3-a]quinoxalines have been obtained.For Communication XV, see [10].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 981–985, July, 1970.     

Synthesis,properties and crystal structure of a heteropoly compound containing titanium

K4H2CoW12O40·2TiO2·9H2O crystallizes from an aqueous solution of Na2WO4, Co(OAc)2 and Ti(SO4)2. The compound has very similar i.r. and u.v. spectra to those of [CoW12O40]6– and [CoW11TiO40]8– but its polarographic behaviour is different from that of [CoW11TiO40]8– and exhibits only reduction of tungsten(VI). A single crystal structural analysis indicates that this compound consists of the heteropolyanion [CoW12O40]6–, titanium–oxygen chain, potassium ions and water molecules.     

Adsoprtion and adsorptive separations: A bibliographical update (1992–1993)

This article provides a bibliographic listing of published journal papers concerned with adsorptive separations during 1992–1993. The references are taken from the 40 most important chemical engineering journals. This paper provides an update to the literature as provided in previous bibliographic papers [1, 2]. These previous papers also included membrane-type separations, however due to the number of papers and the diversity of membrane and associated processes, this material is to be published separately [3].Other bibliographic papers covering the more traditional unit operations, e.g. distillation [4], and equilibrium-staged separations in general [5, 6] have been published. Liquid-liquid extraction [7] is the subject of a separate bibliography (for 1992–1993), due to the number of publications on this topic. A bibliography detailing supercritical extraction from 1980–1993 is also to be published separately due to the current interest in this relatively new technology [8]. A complete bibliography of the chemical engineering journal literature from 1967–1993 has been published by the author [9–12]. An earlier bibliography [13] provides access to the literature prior to 1967.     

Kinetics of the anation reaction of pentaamineaquacobalt(III) by phosphorous acid/hydrogenphosphite

Summary The kinetics of the anation reaction of [Co(NH₃)₅H₂O]³⁺ by H₃PO₃/H₂PO ₃ ^– , to give [CoH₂PO₃(NH₃)₅]²⁺, have been studied at 60, 70 and 80°C, in the acidity range [H⁺](M)=1.5 · 10^–1 –2.0 · 10^–3. Only H₂PO₃ is found to be reactive. The rate data is consistent with an I_d mechanism. The mean value of outer sphere association of [Co(NH₃)H₂O]³⁺ with H₂PO ₃ ^– is 1.5 M^–1. Values of the interchange constants are: 10⁴4k_i(s^–1)= 0.29, 1.47, 5.13, at 60, 70 and 80 °C respectively (H= 1.4 · 10²KJmol^–1, S=8.3 · 10 JK^–1 mol^–1). The first acidity constant of H₃PO₃ at I=1.0 has also been determined: 10²K_a(M)=4.8, 5.2 and 5.5, at 25, 40 and 50 °C respectively.     

Conductometric Determination of the Stability Constants of the Inclusion Complexes of Alkali Cations with [22-DD] Diaza Crown Ether, [211] and [221] Cryptands in Acetonitrile

An equilibrium study concerning the association of Na⁺, K⁺, Rb⁺ and Cs⁺ with 4, 7, 13, 18-tetraoxa-1,10-diazabicyclo [8, 5, 5]-eicosane [211], 4, 7, 13, 16, 21-pentaoxa-1, 10-diazabicyclo [8, 8, 5]-tricosane [221] and 4, 13-didecyl-1, 7, 10, 16-tetraoxa-4, 13-diazacyclooctadecane [22-DD] in acetonitrile has been carried out at 25 °C by using a conductometric technique. The observed molar conductivity, Λ, of a test solution was found to decrease significantly for mole ratios less than 1:1 upon the addition of the complexing ligand. A model based on 1:1 stoichiometry has been used to analyze the conductivity data. The data have been fitted according to a non-linear least-squares analysis that provides the stability constant, K, and the molar conductivity, Λ_c, for each cation – ligand inclusion complex. The binding sequences were found to follow the order: Na⁺ > K⁺ > Rb⁺ ≫ Cs⁺ (K ≈ 0) for [211], Na⁺ > K⁺ > Rb⁺ > Cs⁺ for [221] and K⁺ > Na⁺ > Rb⁺ > Cs⁺ for [22-DD] complexes. Trends in ionic conductivities of complexed ions are also discussed.     

Reactions of coordinated ligands,part II1). Kinetics of iodination of salicylate in bis(ethylenediamine)(salicylato)cobalt(III) cation

Summary The rates of iodination of Salicylate in the bis-(ethylenediamine)(salicylato)cobalt(lII) complex and free Salicylate have been measured in acetate buffer at 40° and I = 0.1 M. The reaction is catalysed by acetate and water. The reactivity order for both acetate- and water-catalysed paths is: [HSal]^– < [(en)₂CoSal]⁺ < [Sal]^2–, where [HSaI]^– and [Sal]^2– stand for the phenol and phenate forms of Salicylate respectively. Chelation of [Sal]^2– to cobalt(III) results in a rate reduction of its iodination by 10⁷.     

Purines,pyrimidines, and condensed systems based on them

The action of various oxidizing agents on 7- and 9-aminotheophyllines and also on 1-methyl-9-aminoxanthine was studied. 7-Aminotheophyllines are oxidized by almost all the oxidizing agents to 6,8-dimethylpyrimido[4,5-e]-as-triazine-5, 7(6H,8H)-dione (40–90%). 1-Methyl-9-aminoxanthine and 9-aminotheophylline are oxidized with greater difficulty. The best results are obtained with hydrogen peroxide, which transforms these amines with yields of –40% into the antibiotics rheumycin and fervenulin, respectively. Under certain conditions the action of bromine and nitric acid leads to the bromination and nitration of the N-aminoxanthines at position 8. A series of the physicochemical characteristics of the N-aminoxanthines were investigated. The factors which affect their behavior toward oxidizing agents and electrophiles are discussed.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 95–102, January, 1989.     

Kinetics and mechanism of osmium(VIII) mediated cerium(IV) oxidation of dimethylsulfoxide in aqueous sulfuric acid

Under the experimental conditions [DMSO]T [CeIV]T [Os]T the kinetics of oxidation of dimethylsulfoxide (DMSO) to dimethylsulfone (DMSO2) have been followed at different temperatures (40–55°C) in 1.0 mol dm–3 sulfuric acid media. The rate of disappearance of [CeIV] shows a first-order dependence on both [Os]T and [DMSO]T and zeroth-order kinetics with respect to [CeIV]. The suggested mechanism involves oxidation of DMSO by OsVIII in a rate-determining step through an outer-sphere mechanism, followed by rapid regeneration of OsVIII by CeIV from OsVI. The rate law conforms to: –d[CeIV]/dt=k0=k[Os]T[DMSO]T. The values of k and the activation parameters are: 102k=(4.9 ± 0.10) mol–1 dm3 s–1 at 40°C, [H2SO4] =1.0 mol dm–3;H=58±3kJmol–1, S= –88 ±5JK–1mol–1.     

Solubility of Solid 2,3-Dimethylbutane and Cyclopentane in Liquid Argon and Nitrogen at the Standard Boiling Points of the Solvents

The solubilities of solid 2,3-dimethylbutane and cyclopentene in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in solutes. The experimental value of the mole fraction solubility of solid 2,3-dimethyl-butane in liquid argon at 87.3 K is (8.26 ± 1.60) × 10^–6 and (2.77 ± 0.94) × 10^–8 in liquid nitrogen at 77.4 K. The experimental value of the mole fraction solubility of solid cyclopentene in liquid argon at 87.3 K is (5.11 ± 0.44) × 10^–6 and (4.60 ± 0.76) × 10^–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbons in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l ₁₂ were also calculated. At 90.0 K liquid argon is a better solvent for investigated solid hydrocarbons than is liquid nitrogen.     

Synthesis and properties of oxazolo[3,2-f]xanthines

Oxazolo[3,2-f]xanthines were synthesized by the reaction of 7-acylalkyl-8-bromo-3-methyl- and -1,3-dimethylxanthines with sodium benzoate in dimethylformamide. Their alkylation with methyl iodine was studied. The reaction of oxazolo[3,2-f]xanthines with primary amines leads to the previously described imidazo[1,2-f]xanthines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 534–537, April, 1988.     

A comparative kinetic study of iridium(III) catalysis in cerium(IV) oxidation of dioxane in aqueous sulfuric acid and perchloric acid media

The kinetics and mechanism of IrIII-catalysed oxidation of dioxane by CeIV in both aqueous H2SO4 and HClO4 media have been studied at different temperatures under the conditions: [dioxane]T [CeIV]T [Ir]T (ca. 10–6–10–8moldm–3). In aqueous HClO4 media a slow uncatalysed path exists alongside the catalysed path, while in aqueous H2SO4 media the catalysed path is the only kinetically detectable path. In both media, the overall process shows a first-order dependence on [CeIV]T; the catalytic path is first order in [Ir]T and exhibits a non-linear dependence on [dioxane]T. The catalysed path probably involves a pre-equilibrium interaction between the catalyst and substrate leading to an outer-sphere complex followed by the electron transfer in the rate-determining step involving CeIV and an outer-sphere complex formed in pre-equilibrium steps. The catalytic path presumably involves the IrIII/IrIV cycle. In HClO4 media the catalytic efficiency is greater than in H2SO4 media. Activation parameters for different paths have been determined in order to rationalise the mechanistic steps.     

Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L=Cysteine and related thiolates

Complexes of the [RuIII(edta)SR]n series, with SR–= deprotonated cysteine, N- acetylcysteine, 2–mercaptoethanol, glutathione and penicilamine, were prepared from [Ru(edta)H2O]– and the corresponding RSH thiols, at pH=5.5. The complexes exhibit intense visible absorption bands at ca. 520nm (3500M–1 cm–1), associated with LMCT from the sulfur ligands bound to RuIII. The kinetics of the formation reactions were first order in [RuIII(edta)H2O]– and thiol reactants, with k1 values ca. 1–5×102 M–1s–1 (25°C) for all the sulfur ligands except penicilamine, which reacted slower by a factor of 10. Activation parameters suggest an associative mechanism, as for the coordination of other S- and N-bound ligands to [RuIII(edta)H2O]–. A reactivity decrease is apparent at low and high pH's (ranges 1–3 and 8–10, respectively), associated with acid-base equilibria involving the less reactive [RuIII(Hedta)H2O] and [RuIII(edta)OH]2– species. A significant rate increase was found for cysteine and penicilamine at ca. pH=8.0, because the thiol reactants deprotonate. The equilibrium constants for all the ligands showed that robust complexes were formed, with K=ca. 1×105 M–1 (25°C). The dissociation rate constants, k–1, were in the 10–3–10–4 s–1 range. The influence of nucleophilic and steric effects increasing and decreasing the formation rates, respectively, is discussed for the thiolate ligands, with adequate comparisons with other L species bound to [RuIII(edta)H2O]–.     

Cyclocondensation of 4-hydroxy-5,6-diaminopyrimidine with α,β-dihalochalcones

The condensation of 4-hydroxy-5,6-diaminopyrimidine with 1,3-diaryl-2,3-dihalopropanones and with dibenzoylacetylenes was used to obtain derivatives of 1H-pyrimido[4,5-b]-1,5-diazepine and pyrimido[4,5-b]pyrazine, respectively. Their spectral characteristics were studied, and the directions in the formation of 7- and 6-membered heterocycles were determined. The synthesized pyrimido[4,5-b]pyrazines exist in the form of two tautomeric species — enaminocarbinol and enol forms, with an intramolecular hydrogen bond of the chelate type.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1409–1414, October, 1993.     

Acid dissociation constants of some nitrogen-containing multinuclear systems

The pK_a values have been determined spectrometrically of the 5, 8, 8-trimethyl-2, 4, 6-trioxo-1, 2, 3, 4, 5, 6, 7, 8, 9, 10-decahydropyrimido[4, 5-b]quinolines Ia–Ic, the 5, 8, 8-trimethyl-2, 4, 6-trioxo-1, 2, 3, 4, 6, 7, 8 9-octahydropyrimido [4, 5-b]quinolines IIa and IIb, the 2, 4, 6-trioxo-5-phenyl-1, 2, 3, 4, 5, 11-hexahydro-11-azapyrimido [4, 5-b]fluorenes IIIa–IIIc, and the 4-amino uracils IVa–IVc. The following sequences of the dissociation of the protons attached to the nitrogen atoms have been established: for I, N₍₁₎ > N₍₁₀₎ > N₍₃₎; for II, N₍₁₎ > N₍₃₎; for III, N₍₁₁₎ > N₍₁₎ > N₍₃₎; and for IV, N₍₃₎ > N₍₁₎.     

Condensed heterocycles with a thiazole nucleus. 8. Thiazolo[4,3-a]pyrimido[5,4-e]pyrimidines

Condensation of 4-amino-2-methylthiothiazolium salts with 2,4,6-trichloro-5-formylpyrimidine or 3-R-2,4-dioxo-6-chloro-5-formyl-1,2,3,4-tetrahydropyrimidines yielded mesoionic derivatives of a new heterocyclic system — thiazolo[3,4-a]pyrimido[5,4-e]-pyrimidine — which can be used for the synthesis of polymethine dyes. The absorption maxima of these dyes are bathochromically shifted by 10–20 nm relative to the maxima of the thiazolopyrimidine analogs. The structure of the compounds synthesized was demonstrated by the PMR and IR spectra.For communication 7, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1126–1128, August, 1984.     

Initial state and transition state solvation in substitution at the square-planar complexes, [PtCl4]2− and [Pd(Et4dien)Cl]+

Summary Rate constants have been determined for the reaction of [PtCl₄]^2– with cyanide in water and in 20% and 40% (v/v) methanol, and for the reaction of [Pd(Et₄dien)Cl]⁺ with thiourea in water, in 50% methanol, and in 50% DMSO, in all cases at 298.2K. The solubility of K₂PtCl₄ has been determined in water and in 20% and 40% methanol; the solubility of [Pd(Et₄dien)Cl]Cl has been determined in water, in 20%, 40%, 60%, and 80% methanol, and in 40% and 80% DMSO; again in all cases at 298.2K. From these solubilities, Gibbs free energies of transfer for the [PtCl₄]^2– and [Pd(Et₄dien)Cl]⁺ ions have been estimated. From these transfer data, published transfer data for cyanide and thiourea, and these and earlier kinetic results, solvent effects on reactivity have been dissected into their initial state and transition state components for the following four reactions: [PtCl₄]^2– hydrolysis, [PtCl₄]^2– plus cyanide, [Pd(Et₄dien)Cl]⁺ substitution, and [Pd(Et₄-dien)Cl]⁺ plus thiourea. The patterns thus established are discussed, and compared with those previously obtained for some other reactions of transition metal complexes.     

Preparation,characterization and electrical conductivity of new heterobimetallic chalcogenates and their 1,10-phenanthroline adducts

New mixed metal chalcogenate coordination polymers, MPb(SCN)₂(SeCN)₂ [M = Co^II, Ni^II or Hg^II], Ag₂-Pb(SCN)₂(SeCN)₂, and the complex heterobimetallic salts, [M(phen)₃][Pb(SCN)₂(SeCN)₂][M = Co^II or Ni^II; phen = 1,10-phenanthroline] that have been prepared and characterized by elemental analyses, i.r. and u.v.–vis. spectra, and by powder XRD patterns. Their solid state electrical conductivities have been investigated, show _rt in the 10^–10–10^–6 S cm^–1 range, and semiconduct at 313–383 K with band gaps in the 0.28–0.91 eV range. [Co(phen)₃][Pb(SCN)₂(SeCN)₂], exhibits a remarkable increase, i.e. 10⁴ order of magnitude, in conductivity at higher temperature, which reflects a disordered metallic system where charge carriers have difficulty in crossing the non-conducting barrier at low temperature.     

Analysis methods for identifying coordinated movements during ligand unbinding

Molecular dynamics simulations have been applied to unbind biological ligands from their receptors [1–5]. Conformation changes are observed in the biomolecules during unbinding, but there exists no systematic method to detect these conformation changes. In this work, we have used `essential dynamics' (ED) [6–7] and projection to latent structures (PLS) [8] to investigate the conformation changes of the bovine serum retinol-binding protein when retinol unbinds from its receptor site. The results of these analyses characterise a large proportion of the movements that occur during unbinding. We find that the loop regions of retinol-binding protein exhibit the largest movements during unbinding. The sudden changes in unbinding speed during the unbinding process appear not to be caused by sudden changes in protein structure.     

Analogs of oxytocin with L- and D-pentafluorophenylalanines in the second position

Summary 1. The separation of pentafluorophenylalanine into optical antipodes has been effected.2. Two new analogs of oxytocin — [2-L-pentafluorophenylalanine]oxytocin and [2-D-pentafluorophenylalanine]oxytocin — have been synthesized and their uterotonic activities have been studied.3. It has been shown that donor — acceptor interaction plays a fundamental role in the stimulation of the biological effect.A. A. Zhdanov Leningrad State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 392–398, May–June, 1977.     

Redox chemistry of [Fe2(CN)10]4−. Part 5. Reaction with thiourea

The reaction of the dimeric iron(III) complex [Fe2(CN)10]4– with a large excess of thiourea, tu, takes place in a series of stages, the first two of which have been examined in detail. The first stage is a one equivalent outer sphere electron transfer to form [Fe2– (CN)10]5– and the radical cation tu+· which dimerises to form the disulfide tu22+. There is kinetic evidence for the formation of a significant proportion of a precursor complex [Fe2(CN)10]4–·tu at high concentrations of tu. The second stage involves cleavage of the mixed valence dimer to yield [Fe(CN)5tu]2– and [Fe(CN)5H2O]3–. On standing, substitution of H2O by tu and oxidation by air occurs slowly, and finally all of the original iron is observed as [Fe(CN)5tu]2–.