Showing papers in "Canadian Journal of Chemistry in 1978"
TL;DR: In this paper, an internally consistent set of pKa values for the strong mineral acids and the arenesulfonic acids were derived by combining various kinds of evidence from the literature.
Abstract: By combining various kinds of evidence from the literature it is possible to derive an internally consistent set of pKa values for the strong mineral acids and the arenesulfonic acids; the values a
303 citations
TL;DR: In this article, the nuclear magnetic resonance spectra of diastereomeric C-24 alkyl sterols have been assigned, based on the chemical shifts of side-chain carbons.
Abstract: 13C nuclear magnetic resonance spectra of diastereomeric C-24 alkyl sterols have been assigned. Differences in the chemical shifts of side-chain carbons permitted the determination of the absolute ...
275 citations
TL;DR: The ladder of ΔG10 determinations obtained from measurements of some 110 gas phase proton transfer equilibria A1−ΔG10 as discussed by the authors was derived from measurements from some 60 acids AH and connecting to the standar.
Abstract: The complete ladder of ΔG10 determinations obtained from measurements of some 110 gas phase proton transfer equilibria A1− + A2H = A1H + A2− involving some 60 acids AH and connecting to the standar...
212 citations
TL;DR: The synthesis of oligonucleotides derived from uridine and adenosine using the tert-butyldimethylsilyl protecting group and the trichloroethylphosphorodichloridite condensation procedure was described in this paper.
Abstract: The synthesis of oligonucleotides derived from uridine and adenosine using the tert-butyldimethylsilyl protecting group and the trichloroethylphosphorodichloridite condensation procedure is describ...
187 citations
TL;DR: In this paper, the assignments of the hydroxyl, hydroperoxyl, and alkyl-peroxideyl radical spin adducts of α-phenyl N-tert-butyl nitrone (PBN) are discussed.
Abstract: The assignments of the hydroxyl, hydroperoxyl, and alkylperoxyl radical spin adducts of α-phenyl N-tert-butyl nitrone (PBN) are discussed. Results of new experiments designed to test the assignment...
144 citations
TL;DR: The antifungal antibiotic Rapamycin crystallises in the orthorhombic space group P212121 with a"="34.85(2), b" ="13.08(1), c''="12.25(1)''.
Abstract: The antifungal antibiotic Rapamycin crystallises in the orthorhombic space group P212121 with a = 34.85(2), b = 13.08(1), c = 12.25(1) A. The molecular structure has been determined by X-ray crysta...
127 citations
TL;DR: In this article, the thermodynamic pair interaction parameters of the ternary systems electrolyte (alkali halides and tetraalkylammonium bromides) and nonelectrolyte (n-alcohols and tert-butylalcohol) were measured at 25 °C through enthalpies of solution, of mixing and of dilution, densities and heat capacities per unit volume.
Abstract: The thermodynamic pair interaction parameters of the ternary systems electrolyte (alkali halides and tetraalkylammonium bromides)–nonelectrolyte (n-alcohols and tert-butylalcohol)–water were measured at 25 °C through enthalpies of solution, of mixing and of dilution, densities and heat capacities per unit volume. Some freezing point and electromotive force data were also combined with previously published data to obtain free energies. From these pair parameters the complete thermodynamics of the salting in and salting out of alcohols can be derived and were used to test various theoretical approaches. Most results are consistent with the cosphere overlap structural model, and the various trends can also be correlated through the scaled-particle theory.
120 citations
TL;DR: In this article, the apparent molal volumes and beat capacities of oligopeptides of glycine, alanine, and serine have been determined in water at 25 °C by flow densimetry and flow microcalorimetry.
Abstract: The apparent molal volumes and beat capacities of oligopeptides of glycine, alanine, and serine have been determined in water at 25 °C by flow densimetry and flow microcalorimetry. The data are reported for the homologous series: glycine to pentaglycine, L-alanine to tetra-L-alanine and L-serine to tri-L-serine. From the limiting and values of the glycine oligomers, the contributions of the glycyl residue in an extended polypeptide chain has been evaluated as: and The data for the other peptides are discussed in terms of contributions from the amino acid side chains, i.e. —CH3 and —CH2OH, and end-group hydration effects. Some necessary conditions for obtaining useful additivity schemes for predicting and of extended polypeptides and proteins are indicated.
100 citations
TL;DR: In this paper, the fluorescence decay of aqueous tryptophan is described by a two exponential decay function whose components have life-times of 3.14 and 0.51
Abstract: The fluorescence decay of aqueous tryptophan is shown to be described by a two exponential decay function whose components have life-times of 3.14 ns and 0.51 ns. These components are assigned as t...
98 citations
TL;DR: Methyl β-cellobioside (2) has been deuterated at positions C-2, -3, - 3′, -4, -6, and -6′ by 1H-2H exchange with deuterium oxide in the presence of Raney nickel catalyst.
Abstract: Methyl β-cellobioside (2) has been deuterated at positions C-2, -3, -3′, -4, -6, and -6′ by 1H–2H exchange with deuterium oxide in the presence of Raney nickel catalyst. The resulting simplificatio...
95 citations
TL;DR: The carbon magnetic resonance spectra of a series of C-19 hydroxy, C-5β,6β epoxy and C-24 ethyl steroids have been assigned in this paper.
Abstract: The carbon magnetic resonance spectra of a series of C-19 hydroxy, C-5β,6β epoxy, C-5α,6α epoxy, and C-24 ethyl steroids have been assigned. Shift parameters for the C-19 hydroxyl function are listed. The data presented has led to a reassignment of the published spectra of several C5α,6 α epoxy steroids. In addition, 13Cmr spectral data for several bicyclic enones and a Δ5(10)-3-estrone are presented.
TL;DR: Fluorescence attributable to the tyrosinate form of the amino acid tyrosine has been observed at neutral pH in the presence of high buffer base concentrations, and this observation is consistent with the large shift in pK(Sl) predicted from absorption measurements and confirms that proton transfer is indeed a mechanism by which carboxylate ions quench tyrosin fluorescence.
Abstract: Fluorescence attributable to the tyrosinate form of the amino acid tyrosine, previously only observed at pH > pK(S0) = 10.3 where tyrosinate exists in the ground state, has been observed at neutral...
TL;DR: In this paper, heat capacities and densities of aqueous solution of 11 1:1 electrolytes were measured at 25 °C with flow calorimeters and densimeters.
Abstract: Measurements at 25 °C with flow calorimeters and densimeters have led to heat capacities and densities of aqueous solutions of 11 1:1 electrolytes: NaClO3, NaBrO3, NaIO3, NaNO3, NaClO4, NH4NO3, KCl...
TL;DR: In this paper, a set of equilibrium constants for aldol condensations of acetaldehyde, acetone, acetophenone, and acetic acid as nucleophiles is given.
Abstract: A set of equilibrium constants for aldol condensations of acetaldehyde, acetone, acetophenone, and acetic acid as nucleophiles and formaldehyde, acetaldehyde, benzaldehyde, acetone, and acetophenon...
TL;DR: In this article, the metal complexes of water-soluble and other porphyrins have been prepared by a heterogeneous reaction with the metal reactant present in an insoluble form.
Abstract: Metal complexes of water-soluble and other porphyrins have been prepared by a heterogeneous reaction with the metal reactant present in an insoluble form. The oxidation state of the metal is important in the reactions. Metal reactants in the lower oxidation states (0, I, II) react with porphyrins but those in the higher oxidation states (III, IV) do not. Metalloporphyrins of high purity may be conveniently prepared by this method.
TL;DR: The densities and heat capacities per unit volume of aqueous solutions of propionamide, methylacetate, ethylacetate and methylethylketone were measured in this article.
Abstract: The densities and heat capacities per unit volume of aqueous solutions of propionamide, methylacetate, ethylacetate, methylethylketone and diethylketone, and bis(2-ethoxyethyl)ether were measured o...
TL;DR: In this article, the chromous chloride promoted addition of N-chlorocarbamates and N -chlorocarboxamides to 1-methoxycyclohexene, ethoxyethylene, dihydropyran, and (1-methylenandrost-4-en-3-one gave, in 60 to 85% yields, either α-acyloxy- or α -acylamino ketals and acetals, or the corresponding ketones and aldehydes depending on the work-up conditions.
Abstract: The chromous chloride promoted addition of N-chlorocarbamates and N-chlorocarboxamides to 1-methoxycyclohexene, ethoxyethylene, dihydropyran, and (1-methoxyethylidene)-cyclohexane gave, in 60 to 85% yields, either α-acyloxy- or α-acylamino ketals and acetals, or the corresponding ketones and aldehydes depending on the work-up conditions. The regio-specificity of the addition was higher with the first two enol ethers (≥97%) than with the latter two (≥85%). N-Chlorourethane was added to 17-methoxymethylenandrost-4-en-3-one (19) and the sole addition product isolated was the 17α-chloro-20-ethoxycarbonylamino derivative 20 in 75% yield. Additions to triacetyl-D-glucal and 3-O-acetyl-4,6-O-benzylidene-D-glucal followed by solvolysis under Koenigs–Knorr conditions led predominantly to 2-amino-gluco-pyranosides in 30 to 65% yields, whereas additions to 3-O-acetyl-4,6-O-benzylidene-D-allal gave 2-amino altropyranosides in 40 to 56% yields.
TL;DR: Some ab-initio valence-bond wave-functions for π-electrons of the ground states of O3, NO2−, and CH2N2 were reported in this paper.
Abstract: Some ab-initio valence-bond wave-functions are reported for the π-electrons of the ground-states of O3, NO2−, and CH2N2. Examination of these wave-functions provides further support for the hypothe...
TL;DR: The interest in naturally occurring phenol sulfate ester salts has been renewed by modem spectroscopic investigation of these compounds as discussed by the authors, which has led to the development of a number of synthetic methods, plus spectroscopy (uv, ir, 1H nmr, 13C...
Abstract: Renewed interest in naturally occurring phenol sulfate ester salts has necessitated modem spectroscopic investigation of these compounds. Synthetic methods, plus spectroscopic (uv, ir, 1H nmr, 13C ...
TL;DR: The photosensitized (electron transfer) irradiation of cis- and trans-2,3-diphenyloxirane (1 and 2) led to cleavage of the oxirane carbon-carbon bond and subsequent formation of the carbonyl ylide as mentioned in this paper.
Abstract: The photosensitized (electron transfer) irradiation of cis- and trans-2,3-diphenyloxirane (1 and 2) led to cleavage of the oxirane carbon–carbon bond and subsequent formation of the carbonyl ylide....
Abstract: A series of pyrimidine and purine bases bas been studied experimentally by electron spectroscopy for chemical analysis. Individual component peaks in the spectra were assigned on the basis of known...
TL;DR: A partial mechanism for compound I formation is proposed in which the group of pKa 4.15 plays a crucial role in the reactions with both hydrogen peroxide and cyanide.
Abstract: The kinetics of the reactions of hydrogen peroxide and cyanide with native horseradish peroxidase, as well as reactions of compounds I and II with ferrocyanide have been studied in ordinary water and in deuterium oxide at 25 °C and ionic strength 0.11 using a stopped-flow apparatus. Rate constants for all reactions were measured over a wide range of acidity in both solvents from which equilibrium and kinetic isotope effects were evaluated. Protonation of an ionizable group on the enzyme with a pKa value of 4.15 ± 0.05 in water inhibits the reactions with both hydrogen peroxide and cyanide. A significant kinetic isotope effect, kH/kD = 1.6 ± 0.1, was measured for compound I formation whereas no significant kinetic isotope effect was found for cyanide binding. On the basis of these findings, a partial mechanism for compound I formation is proposed in which the group of pKa 4.15 plays a crucial role. The pH dependencies of the ferrocyanide reaction in the pH interval 4.5–10.8 confirmed the role of an acid gr...
TL;DR: A series of nickel-II and copper-II complexes of the title ligand were reported in this article, which appear to exhibit predominantly pseudo-octahedral structures in the solid state.
Abstract: A series of nickel(II) and copper(II) complexes of the title ligand are reported which appear to exhibit predominantly pseudo-octahedral structures in the solid state. Anion bridged dimeric structu...
TL;DR: A simple synthesis of the title compounds, which is more than 10 steps shorter and an order of magnitude more efficient than our recent photochemical synthesis of chasmanine, is described in this paper.
Abstract: A simple synthesis of the title compounds, which is more than 10 steps shorter and an order of magnitude more efficient than our recent photochemical synthesis of chasmanine, is described. The main...
TL;DR: In this paper, a polarographic study of the oxidation mechanism of Lascorbic acid is carried out in a basic medium and two oxidation waves are observed, showing that the limiting current is governed by diffusion and that in each reaction a two electron transfer takes place.
Abstract: A polarographic study of the oxidation mechanism of L-ascorbic acid is carried out in a basic medium and two oxidation waves are observed.An analysis of these waves shows that the limiting current is governed by diffusion and that in each reaction a two electron transfer takes place. On the rising portion of the waves, the oxidation process consists of two consecutive one electron transfers. In the first wave, the second transfer is the rate determining step, whilst in the second wave, a chemical stage subsequent to the second electron transfer is the rate determining step. The reaction orders, together with the Tafel slopes, are calculated.The oxidation mechanism of this acid in basic media is different from that in acid media.
TL;DR: The presence of K in Na2SO4 effects a lowering of both the transition temperature and the enthalpy of transition along with an alteration from the "athermal" kinetic behavior to first-order kinetics.
Abstract: Phase transformation studies on pure Na2SO4 revealed four phases only; phase IV was not observed.Electrical conductivity measurements have been made on polycrystalline undoped and K-doped Na2SO4 and on single crystals of undoped Na2SO4. Kinetic measurements on II → III transformation in undoped Na2SO4 show rate of conversion to be time independent and inversely related to temperature.The presence of K in Na2SO4 effects a lowering of both the transition temperature and the enthalpy of transition along with an alteration from the "athermal" kinetic behavior to first-order kinetics.
TL;DR: In this article, the ECA core line spectra have been obtained for uracil, the thiouracils, and some 1-methyl and 3-methyl analogues.
Abstract: ESCA core line spectra have been obtained for uracil, the thiouracils, and some 1-methyl and 3-methyl analogues In addition, anionsof the mono methyl derivatives have been prepared and studied Co
TL;DR: In this article, the authors measured the densities of water + tetrahydrofuran mixtures at 5'K intervals of temperature from 288.15 to 308.15'K.
Abstract: Densities of water + tetrahydrofuran mixtures were measured at 5 K intervals of temperature from 288.15 to 308.15 K. Excess thermal expansion coefficients and partial molar excess thermal expansivities at 298.15 K over the whole mole fraction range were derived from the results. The significance of the expansivities is discussed in terms of the structural changes accompanying the formation of the mixture.
TL;DR: In this paper, the reaction of ethyl azidoacetate with the monoaldehydes of furan, thiophene and seleno-phene yields furo-, thieno-, and Selenolo[2,3-b]- and [3,2-b]pyrroles.
Abstract: The reaction of ethyl azidoacetate with the monoaldehydes of furan, thiophene and seleno-phene yields furo-, thieno-, and selenolo[2,3-b]- and [3,2-b]pyrroles Only pyrrolo[2,3-b]pyrrole could be prepared by this route using ethyl 4-formylpyrrole-2-carboxylate as the substrate The thieno- and selenolo[3,2-b]pyrroles also could be obtained by the action of ethyl bromoacetate on 3-acetamidothiophene-2-aldehyde, or the corresponding selenolo compound, followed by cyclization of the N-substituted acetamide productsThe nmr, uv, and mass spectra are reeorded for the various products described [Journal translation]
TL;DR: A totally stereospecific synthesis of the insect pheromone, (−)-α-multistriatin, is reported starting from D-glucose.
Abstract: A totally stereospecific synthesis of the insect pheromone, (−)-α-multistriatin, is reported starting from D-glucose.