Showing papers in "Canadian Journal of Chemistry in 1992"
TL;DR: In this paper, Gaussian-type orbital and auxiliary basis sets have been optimized for local spin density functional calculations for boron-neon atoms through neon and xenon.
Abstract: Gaussian-type orbital and auxiliary basis sets have been optimized for local spin density functional calculations This first paper deals with the atoms boron through neon Subsequent papers will provide a list through xenon The basis sets have been tested for their ability to give equilibrium geometries, bond dissociation energies, hydrogenation energies, and dipole moments These results indicate that the present optimization technique yields reliable basis sets for molecular calculations Keywords: Gaussian basis sets, density functional theory, boron–neon, geometries, energies of reactions
2,716 citations
TL;DR: Relativistic compact effective potentials (RCEP) as mentioned in this paper were derived from numerical Dirac-Fock atomic wavefunctions using shape-constrained shapes.
Abstract: Relativistic compact effective potentials (RCEP), which replace the atomic core electrons in molecular calculations, have been derived from numerical Dirac–Fock atomic wavefunctions using shape-con...
1,966 citations
TL;DR: In this paper, a comprehensive tabulation of Cowan-Griffin relativistic core model potentials and valence basis sets corresponding to the abinitio model potential method is presented, which includes those for the elements from Li (Z) to La (Z), the alkaline M+ and alkaline earth M2+ cations, and for the halogen X− anions.
Abstract: A comprehensive tabulation of Cowan–Griffin relativistic abinitio core model potentials and valence basis sets corresponding to the Cowan–Griffin abinitio model potential method is presented. It includes those for the elements from Li (Z = 3) to La (Z = 57), the alkaline M+ and alkaline earth M2+ cations, and for the halogen X− anions. Molecular results are presented in order to test the potentials and basis sets and to estimate the extent of the mass–velocity and Darwin relativistic effects considered within the method, which lie within the expected margins. Keywords: relativistic, model potential, effective core potential, basis sets, abinitio.
198 citations
TL;DR: In this paper, nonbonding repulsive interactions between hydrogen atoms, separated by less than ca. 2.18 A and connected to two carbon atoms in the 1,4 positions, are associated with additional pairs of bond and...
Abstract: Nonbonding repulsive interactions between hydrogen atoms, separated by less than ca. 2.18 A and connected to two carbon atoms in the 1,4-positions, are associated with additional pairs of bond and ...
124 citations
TL;DR: Trichodermalongibrachiatum Rifai aggr. is a fungus reported to be antagonistic to the fungus Mycenacitricolor, the causative agent of the American leaf spot disease of coffee as mentioned in this paper.
Abstract: Trichodermalongibrachiatum Rifai aggr. is a fungus reported to be antagonistic to the fungus Mycenacitricolor, the causative agent of the American leaf spot disease of coffee. We have investigated ...
106 citations
TL;DR: In this paper, the authors investigated the enthalpically driven copigmentation of malvin (a common anthocyanic pigment) with a series of naturally occurring colourless organic molecules (copigments).
Abstract: Copigmentation of malvin (a common anthocyanic pigment) with a series of naturally occurring colourless organic molecules (copigments) has been investigated by UV–visible absorption. The temperature-dependence of the visible spectrum of the copigmented solutions yields the copigmentation enthalpy and entropy changes. The experiments are carried out at pH 3.5 (malvin flavylium cation copigmentation) and pH 5.5 (copigmentation of the malvin quinonoidal bases). Copigmentation appears to be clearly enthalpically driven (exothermic process with unfavourable entropy change) in the case of chlorogenic acid and (+)-catechin. Concerning caffeine and tryptophan, favourable entropy changes, probably arising from solvation effects, have been recorded. Similar experiments in water–ethanol binary solvents have shown that the dramatic weakening of copigmentation on cosolvent addition is essentially entropic in origin. Salt effects on copigmentation have been investigated as well. Most of the results are discussed with a...
97 citations
TL;DR: An overview of the strategy used to come up with the design of a new type of ligand that is appropriate for coordination to both the late metals and the early metals is given in this paper.
Abstract: An overview is given on the strategy used to come up with the design of a new type of ligand that is appropriate for coordination to both the late metals and the early metals. The coordination chem...
97 citations
TL;DR: In this paper, the structures of the major glycine conformers and several transition state structures were optimized at HF/6-31G* and HF/ 6-31 G* levels of theory.
Abstract: The structures of the major glycine conformers, and several transition state structures, were optimized at HF/6-31G* and HF/6-31 + G* levels of theory and the correlation energies were calculated at MP2/6-31G* and MP2/6-31 + G** levels on these geometries, respectively. The heat of formation of gas phase glycine is calculated to be. Thermodynamic properties, etc. are calculated as functions of temperature using standard statistical thermodynamic methods. MP2/6-31 + G* optimization was carried out on the zwitterion, found by HF/6-31 + G* optimization to be a local minimum. The results suggest that glycine in the zwitterionic form in the gas phase is not a stationary point. Zwitterionic glycine does not exist in the gas phase.
94 citations
TL;DR: The energies, geometries, and charge distributions of the closo-, nido-, and arachno-boranes and closo-carboranes were determined in SCF calculations using a contracted (9s,5p) basis set of Huzinaga as mentioned in this paper.
Abstract: The energies, geometries, and charge distributions of the closo-, nido-, and arachno-boranes and closo-carboranes are determined in SCF calculations using a contracted (9s,5p) basis set of Huzinaga...
94 citations
TL;DR: In this paper, the rate law of perchloric acid was shown to hold for L-rhamnose and D-mannose by Cr(VI) in perchlorated acid.
Abstract: The oxidation of L-rhamnose and D-mannose by Cr(VI) in perchloric acid follows the rate law:K = 5.40, k0 = 0.00138 M−1 s−1, k1 = 6.71 × 10−4 M−3 s−1 for D-mannose and K = 2.63, k0 = 2.51 × 10−3 M−1...
68 citations
TL;DR: In this article, a quantitative study of the equilibria involved in the interaction of Cu(II) ion with D-glucoheptonic, D-glucuronic and D-galacturonic acids in aqueous medium has been carried out by means of potentiometric measurements of hydrogen ion concentrations at a constant temperature of 20 °C and an ionic strength of 0.10 (NaNO3).
Abstract: A quantitative study of the equilibria involved in the interaction of Cu(II) ion with D-glucoheptonic, D-gluconic, D-galactonic, D-ribonic, D-glucuronic, and D-galacturonic acids in aqueous medium has been carried out by means of potentiometric measurements of hydrogen ion concentrations at a constant temperature of 20 °C and an ionic strength of 0.10 (NaNO3). The equilibrium data were processed with the FORTRAN computer program BEST. It was found that Cu(II) interacts with D-aldonic acids to form 1:1, 2:2, and 1:2 (M/L) complexes. The copper(II) complexes with D-galacturonic and D-glucuronic acids are considerably weaker than those of D-aldonic acid. Possible structures of the complex species formed are discussed.
TL;DR: In this paper, an abinitio self-consistent field molecular orbital approach was used to compute 3-21G/STO-3G* electrostatic potentials and average local ionization energies for 17 para-substituted anilines.
Abstract: Using an abinitio self-consistent-field molecular orbital approach, we computed 3-21G//STO-3G* and STO-5G//STO-3G* electrostatic potentials and average local ionization energies for 17 para-substituted anilines. Our results demonstrate that the most negative potentials (Vmin) and the local surface ionization energy minima (ĪS,min) associated with the amine nitrogen lone pairs are highly sensitive indicators of the electron-donating and electron-attracting tendencies of the para substituents. We find excellent linear relationships between the 3-21G//STO-3G* amine nitrogen Vmin and ĪS,min and the σp0 Hammett constants of the substituent X; the correlation coefficients are 0.99. Correlations of slightly lesser quality are shown to exist between Vmin, ĪS,min, and σp−, σp, and pKa. Estimates of previously unknown σp0 and pKa values are given. The presence of ring carbon ĪS,minmeta to the substituent X also provides a predictive capability for determining σm values.
TL;DR: It is well known that the infinite Kramers-Kronig transform is equivalent to the infinite Hilbert transform, which is the equivalent of the allied Fourier integrals as discussed by the authors.
Abstract: It is well known that the infinite Kramers–Kronig transform is equivalent to the infinite Hilbert transform, which is equivalent to the allied Fourier integrals. The Hilbert transform can thus be i...
TL;DR: In this paper, the fundamental reactions of DMPO have been thoroughly investigated in terms of ESR signals obtained in a Fenton system with a spin trap, 5,5-dimethyl-1-pyrroline-Noxide (DMPO).
Abstract: To assign unidentified ESR signals obtained in a Fenton system with a spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), fundamental reactions of DMPO have been thoroughly investigated. When the c...
TL;DR: In this article, the transition state and barrier height for rearrangement of nitromethane to methyl nitrite were determined for CH3NO2, CH3ONO, dissociat...
Abstract: Calculations designed to characterize the transition state and determine the barrier height for rearrangement of nitromethane to methyl nitrite are reported. Structures of CH3NO2, CH3ONO, dissociat...
TL;DR: In this paper, the thermal and 254-nm photochemical dissolution reactions of magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (α-Fe 2O3) suspended in EDTA aqueous solutions were compared.
Abstract: The thermal and 254-nm photochemical dissolution reactions of magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (α-Fe2O3) suspended in EDTA aqueous solutions were compared. γ-Fe2O3 and Fe3O4 are...
TL;DR: The electronic and geometric structures of paramagnetic iron dinitrosyl complexes have been investigated using electron spin resonance, infrared spectroscopy, and X-ray crystallography.
Abstract: The electronic and geometric structures of paramagnetic iron dinitrosyl complexes have been investigated using electron spin resonance, infrared spectroscopy, and X-ray crystallography. It is concluded that these compounds are best described as 17 electron complexes with a d9 configuration rather than the d7 configuration assumed by most previous investigators. The anisotropy of the g values, determined from the electron spin resonance spectra of frozen solutions, varies considerably from complex to complex. The results are consistent with the supposition that all of the complexes have a distorted tetrahedral geometry, but the nature of the distortion changes as the ligands are varied. As a result of this variation there are changes in the nature of the spin-containing d orbital. Ligands containing hard, nonpolarizable donor atoms such as oxygen or fluorine produce a distortion towards a planar geometry, placing the odd electron in a predominantly orbital, while those containing softer donor atoms such as...
TL;DR: The base-catalyzed cycloaddition and double Michael cyclization of substituted Nazarov reagents and of 1-phenylsulfinyl analogs, with 2-carbomethoxy-2-cyclohexen-1-one yielding cis-decalins is described in this article.
Abstract: The base-catalyzed cycloaddition and double Michael cyclization of substituted Nazarov reagents and of 1-phenylsulfinyl analogs, with 2-carbomethoxy-2-cyclohexen-1-one 1 yielding cis-decalins is re...
TL;DR: The reaction of trimethylpyrazole (tmpzH) with copper metal shot in air yields a mixture of the trinuclear copper(I) complex [Cu(tmpz)]3, 1, and the binuclear copper (I/II) complex[Cu(3-CO2dmpz)( tmpzH)]2Cu, 2 (where dmpz is dimethyl pyrazolate) Crystals of 1 are monoclinic, a
Abstract: The reaction of molten trimethylpyrazole (tmpzH) with copper metal shot in air yields a mixture of the trinuclear copper(I) complex [Cu(tmpz)]3, 1, and the trinuclear copper(I/II) complex [Cu(3-CO2dmpz)(tmpzH)]2Cu, 2 (where dmpz is dimethylpyrazolate) Crystals of 1 are monoclinic, a = 8403(3), b = 22453(2), c = 11362(2) A, (3 = 9583(2)°, Z = 4, space group P21/c Crystals of 2 are triclinic, a = 10988(3), b = 11009(2), c = 6457(1) A, α = 10313(2)°, β = 10302(2)°, γ = 10870(2)°, Z = 1, space group The reaction of molten 4-bromodimethylpyrazole (4-BrdmpzH) with copper metal shot in air gave the binuclear copper(II) complex [Cu(4-Br-3-CO)2mepz)(4-BrdmpzH)2]2, 3 (where mepz is methylpyrazolate) There are two crystalline forms of 3:3a, triclinic, a = 10152(3), b = 13068(3), c = 10033(3) A, a = 11238(2)°, (3 = 11646(2)°, γ = 7029(2)°, Z = 1, space group ; and 3b, monoclinic, a = 13470(1), b = 16005(2), c = 20174(1) A, β = 98142(6)°, Z = 4, space group C2/c Magnetic susceptibility studie
TL;DR: This paper showed that 1-phenyl-4H-1,3,2-benzodioxaborins generated the corresponding ortho-quinone methides, which were found to undergo intermolecular cycloaddition reactions with ethyl vinyl ether, dihy...
Abstract: Thermolysis of 1-phenyl-4H-1,3,2-benzodioxaborins generated the corresponding ortho-quinone methides, which were found to undergo intermolecular cycloaddition reactions with ethyl vinyl ether, dihy...
TL;DR: A detailed study of metabolites produced by the plant cell culture line of Tripterygiumwilfordii, a Chinese herbal plant, is presented in this article, where 18 compounds within the diterpene and triterpenes families have been isolated and fully characterized.
Abstract: A detailed study of metabolites produced by the plant cell culture line of Tripterygiumwilfordii, a Chinese herbal plant, is presented. Eighteen compounds within the diterpene and triterpene families have been isolated and fully characterized. Of these, five are novel compounds, and their structures were determined by a combination of spectral analysis, chemical correlation and single crystal X-ray diffraction. The interest of these compounds in the treatment of rheumatoid arthritis, skin allergies, and for male contraception is noted.
TL;DR: In this article, the dibutyltin N-salicylidenevaline complex (Bu2Sn(OC6H4CH=NCH(i-Pr)COO) was characterized by 1H and 13 C NMR, IR, and elemental analysis.
Abstract: Eight new diorganotin complexes formulated as R2Sn(OArCR″=NCHR′COO) were prepared and characterized by 1H and 13 C NMR, IR, and elemental analysis. A single crystal X-ray diffraction study of the dibutyltin N-salicylidenevaline complex, Bu2Sn(OC6H4CH=NCH(i-Pr)COO), determines the molecular structure. The crystals are orthorhombic, space group P212121 with a = 9.187(2) A, b = 10.003(2) A, c = 23.482(4) A, V = 2157.8(6) A3, Z = 4, and Dc = 1.392 g cm−3. The final discrepancy factors are RF = 0.040, and Rw = 0.021 for 1131 significant reflections. The tin atom has a distorted trigonal bipyramidal coordination, with no short intermolecular contacts. The two axial Sn—O bonds of 2.078(10) and 2.151(8) A and the equatorial Sn—N bond of 2.158(8) A are among the shortest found in related complexes. The fact that the closest intermolecular Sn—O distance is 4.511(8) A indicates a nonbridging carbonyl group.
TL;DR: Dibromo- and diiodo[(2-pyridyl)phosphine]palladium(II) complexes are prepared by metathesis of cis-PdCl2(PPh3−npyn)2 species (n n = 1/3) using the appropriate sodium halide; py n = 2pyride;
Abstract: Dibromo- and diiodo[(2-pyridyl)phosphine]palladium(II) complexes are prepared by metathesis of cis-PdCl2(PPh3−npyn)2 species (n = 1–3) using the appropriate sodium halide; py = 2-pyridyl. NMR spect...
TL;DR: The relative potencies of both the monodeoxy and mono-O-methyl derivatives of the Leb-OMe tetrasaccharide (α-L-Fuc-(1'→'2)-β-D-Gal-(1') and β-DglcNAc-Omme) as inhibitors of the com...
Abstract: The relative potencies of both the monodeoxy and mono-O-methyl derivatives of the Leb-OMe tetrasaccharide (α-L-Fuc-(1 → 2)-β-D-Gal-(1 → 3)-[α-L-Fuc-(1 → 4)]-β-D-GlcNAc-OMe) as inhibitors of the com...
TL;DR: The authors extracted mycelia from a 15 L stirred-jar fermentation culture of Fusariumavenaceum (DAOM 196490) and partitioned them between hexane and methanol/water.
Abstract: Dried mycelia from a 15 L stirred-jar fermentation culture of Fusariumavenaceum (DAOM 196490) were extracted with dichloromethane and partitioned between hexane and methanol/water. Recrystallizatio...
TL;DR: Short, efficient, and convergent syntheses of ketorolac (1) based on the inter- or intramolecular oxidative addition of malonyl and substituted malonyls radicals to 2-benzoylpyrrole and derivatives as discussed by the authors.
Abstract: Short, efficient, and convergent syntheses of ketorolac (1) based on the inter- or intramolecular oxidative addition of malonyl and substituted malonyl radicals to 2-benzoylpyrrole and derivatives ...
TL;DR: A theoretical study has been carried out on four σ-bond metathesis reactions mediated by the electron-poor lutetium metal center as discussed by the authors, where the authors combined methods from quantum mechanics and statistical mechanics to obtain enthalpies and entropies of activation as well as transition state structures.
Abstract: A theoretical study has been carried out on four σ-bond metathesis reactions mediated by the electron-poor lutetium metal centre The four processes include hydrogen exchange, X2Lu-H + D2 → X2Lu-D + HD (1), and hydrogenolysis X2Lu-CH3 + H2 → Cl2Lu-H + CH4 (2), in which a H—H bond is activated, as well as methane exchange, X2Lu-CH3 + CH4 → X2Lu-CH3 + CH4 (3), and methylation, Cl2Lu-H + CH4 → X2Lu-CH3 + H2 (4), in which a C—H bond is activated The fragment employed in a number of experimental studies was modelled by Cl2Lu and all calculations were based on approximate Density Functional Theory (DFT) The study combined methods from quantum mechanics and statistical mechanics to obtain enthalpies and entropies of activation as well as transition state structures All four processes were found to have an ordered four-centre transition state with negative entropies of activation given by ΔS≠ = −109(1), −124(2), −131 (3), and −134(4) J mol−1 K−1 at T = 29815 K The Gibb's free energies of activation, ΔG≠(
TL;DR: In this article, the interaction of various monovalent, divalent, and trivalent metal cations with the group of diethyl phosphate in aqueous solution, at metal: phosphate ratios ranging from 1:40 to 6:1.
Abstract: We have studied, using Raman and infrared spectroscopy, the interaction of various monovalent, divalent, and trivalent metal cations with the group of diethyl phosphate in aqueous solution, at metal: phosphate ratios ranging from 1:40 to 6:1. The results show that the metal cations interact with the phosphate groups in various ways and to different extents. Spectral characteristics for some specific types of interactions are presented, namely, for direct metal binding by one of the oxygen atoms in the group, the formation of water-separated ion pairs, and non-specific electrostatic interactions.
TL;DR: Phomopsisconvolvulus is a host-specific pathogen which causes leaf spots and anthracnose lesions in the important perennial weed Convolvusarvensis (field bindweed) as discussed by the authors.
Abstract: Phomopsisconvolvulus is a host-specific pathogen which causes leaf spots and anthracnose lesions in the important perennial weed Convolvulusarvensis (field bindweed). Investigation of the metabolit...
TL;DR: Tropinone (6) was deprotonated with lithium diisopropylamide and with chiral lithium amides (18−24) and the resulting enolates (two enantiomers) were treated with electrophiles as discussed by the authors.
Abstract: Tropinone (6) was deprotonated with lithium diisopropylamide and with chiral lithium amides (18–24) and the resulting enolates (two enantiomers) were treated with electrophiles. The aldol reaction ...