scispace - formally typeset
Search or ask a question

Showing papers in "Canadian Journal of Chemistry in 1993"


Journal ArticleDOI
TL;DR: This review outlines a decade of research that employs quantitative kinetic methods of autooxidation to phospholipids aggregated into membranes that employs the classical rate law for autoxidation.
Abstract: This review outlines a decade of research that employs quantitative kinetic methods of autooxidation to phospholipids aggregated into membranes. The classical rate law for autoxidation:was found to...

153 citations


Journal ArticleDOI
TL;DR: In this paper, practical and simple techniques for using nonmodified domestic microwave ovens as safe and convenient laboratory devices to obtain numerous esters were described, and high pressures are avoided by condu...
Abstract: Practical and simple techniques are described for using nonmodified domestic microwave ovens as safe and convenient laboratory devices to obtain numerous esters. High pressures are avoided by condu...

132 citations


Journal ArticleDOI
TL;DR: The secondary metabolites produced by the fungus Stachybotrys cylindrospora, which is known to be strongly antagonistic to the blue-stain fungus Ceratocystiopsis crassivaginata, have been examined in this paper.
Abstract: The secondary metabolites produced by the fungus Stachybotrys cylindrospora, which is known to be strongly antagonistic to the blue-stain fungus Ceratocystiopsis crassivaginata, have been examined....

94 citations


Journal ArticleDOI
TL;DR: A kinetic study of the reduction of ferrate ion under basic conditions has been completed in this article, where it was shown that a typical aliphatic ether, tetrahydrofuran, is oxidized at a rate comparable to that of a typical ferrate atom.
Abstract: A kinetic study of the reduction of ferrate ion under basic conditions has been completed. The observation that a typical aliphatic ether, tetrahydrofuran, is oxidized at a rate comparable to that ...

87 citations


Journal ArticleDOI
TL;DR: In this paper, the 13C chemical shifts and some 1H−13C coupling constants of 23 pyrazoles and indazoles were reported and discussed, and the spectra were recorded in CDCl3 and in DMSO-d6 solutions.
Abstract: The 13C chemical shifts and some 1H–13C coupling constants of 23 pyrazoles and indazoles are reported and discussed. The spectra were recorded in CDCl3 and in DMSO-d6 solutions and, in several case...

78 citations


Journal ArticleDOI
TL;DR: In this paper, reactions of certain iridium complexes with catecholborane (HBcat) gave boron-substituent redistribution products with concomitant formation of a complex mixture of iridium hydri...
Abstract: Reactions of certain iridium complexes with catecholborane (HBcat) gave boron-substituent redistribution products ([Bcat2]−, B2cat3) with concomitant formation of a complex mixture of iridium hydri...

66 citations


Journal ArticleDOI
TL;DR: In this paper, the inhibition effect of Mn2+ on the rates of Cr(VI) oxidations of 13 different organic reductants (RH) in aqueous perchloric acid has been studied.
Abstract: The inhibition effect of Mn2+ on the rates of the Cr(VI) oxidations of 13 different organic reductants (RH) in aqueous perchloric acid has been studied. The reductants were formaldehyde, formic aci...

62 citations


Journal ArticleDOI
TL;DR: For a given number of skeletal atoms, the π-electron count of an unsaturated heterocycle can be modified by the incorporation of heteroatoms from different periodic groups as discussed by the authors.
Abstract: For a given number of skeletal atoms, the π-electron count of an unsaturated heterocycle can be modified by the incorporation of heteroatoms from different periodic groups. Sulfur and nitrogen are particularly effective in this regard, as their high electronegativity can stabilize electron-rich π-systems. A variety of aromatic, anti-aromatic, and radical systems can be prepared from admixtures of these elements. While the properties of these ring systems are interesting in their own right, the compounds are not without relevance in the design of new materials. The strong interannular interactions that are developed between these rings in the solid state makes them ideal candidates for the fabrication of molecular conductors. The origins and development of this area of research are the subjects of this presentation.

57 citations


Journal ArticleDOI
TL;DR: The square-planar cations [Pd(CO)4]2+ and [Pt( CO)4]-2+ were shown to exhibit the highest CO stretching frequencies reported so far, about 120 cm−1 higher than in free CO, which suggests the absence or near absence of π-back donation for the M-CO bond as mentioned in this paper.
Abstract: The reductive carbonylation of either platinum(IV) fluorosulfate, Pt(SO3F)4, or palladium(III) fluorosulfate, Pd(SO3F)3, either in solution of fluorosulfuric acid, HSO3F, or in the solid state with CO at pressures of 0.5 to 2 atmospheres and at 25 °C, affords in high yield complexes of the type M(CO)2(SO3F)2, M = Pd or Pt. The square-planar complexes are readily converted by solvolysis in liquid antimony(V) fluoride in the presence of CO at a pressure of about 1 atmosphere to white, thermally stable, salts of the composition [M(CO)4][Sb2F11]2, M = Pd or Pt, which contain the novel, square-planar cations [Pd(CO)4]2+ and [Pt(CO)4]2+. The two cations exhibit the highest CO stretching frequencies reported so far, about 120 cm−1 higher than in free CO, which suggests the absence or near absence of π-back donation for the M—CO bond.

54 citations


Journal ArticleDOI
TL;DR: In this article, absorption and magnetic circular dichroism (MCD) spectra were reported for metallophthalocyanine-N-isologs: magnesium-3,4-pyridinoporphrazine (MgPcN4(−2)), zinc-3.4-polymorphine (ZnPcn4(n)) and ZnPn(n)
Abstract: Absorption and magnetic circular dichroism (MCD) spectra are reported for the metallophthalocyanine-N-isologs: magnesium-3,4-pyridinoporphrazine (MgPcN4(−2)), zinc-3,4-pyridinoporphyrazine (ZnPcN4(...

53 citations


Journal ArticleDOI
TL;DR: The design and syntheses of two cephalosporin–carboplatinum prodrugs that can be released by a β-lactamase are described and these notions provide a new approach to the use of platinum complexes for antitumor therapy.
Abstract: The design and syntheses of two cephalosporin–carboplatinum prodrugs that can be released by a β-lactamase are described. The hydrolysis of cephalosporins catalyzed by a β-lactamase with acetyl or DACCP as 3′-leaving groups is studied by 1H nuclear magnetic resonance in deuterated buffer solutions. These notions provide a new approach to the use of platinum complexes for antitumor therapy.

Journal ArticleDOI
TL;DR: The density, isobaric specific heat capacity, and isentropic compressibility of water-ethanolamine (W-EA) mixtures have been measured at three temperatures (10, 25, and 40 °C) over the entire compo...
Abstract: The density, isobaric specific heat capacity, and isentropic compressibility of water–ethanolamine (W–EA) mixtures have been measured at three temperatures (10, 25, and 40 °C) over the entire compo...

Journal ArticleDOI
TL;DR: In this paper, the derivatives of L-aspartic and L-glutamic acids can be converted into α-hydroxy acids via oxygenation of the corresponding enolates.
Abstract: Derivatives of L-aspartic and L-glutamic acids can be converted into α-hydroxy acids via oxygenation of the corresponding enolates.

Journal ArticleDOI
TL;DR: In this paper, the effects of the indicator-micelle association on the apparent pKa of neutral red with cationic surfactants, viz., N-hexadecylpyridinium chloride and alkyltrimethylammonium bromides, were investigated spectroscopically.
Abstract: The interactions of neutral red with cationic surfactants, viz., N-hexadecylpyridinium chloride and alkyltrimethylammonium bromides; a nonionic surfactant, viz., Triton X100; and an anionic surfactant, viz., sodium dodecyl sulfate, were investigated spectroscopically. The equilibrium constants for the association of the indicator with the micelles were determined from the apparent association constants at constant pH at 298 K. The effects of the indicator-micelle association on the apparent pKa of the indicator in aqueous surfactant solutions are discussed. It was shown that the apparent pKa of the indicator in cationic surfactant solution can be predicted from knowledge of the indicator-micelle association constant.

Journal ArticleDOI
TL;DR: In this article, an experimental and theoretical study of the 600nm band system of phenoxyl and several methoxy substituted compounds was performed. But the authors only used the (ab initio) CASSCF method to simulate the observed vibrational structure adequately.
Abstract: An experimental and theoretical study is reported of the 600 nm band system of phenoxyl and several methoxy substituted phenoxyls. These radicals, generated in freon, show a diffuse band in this region with a vibrational structure that is incompletely resolved but consistent with the 500 cm−1 "progression" observed earlier for phenoxyl in the vapour and in a rigid matrix. The low intensity of this band is considerably enhanced by ortho-methoxy substitution. To establish its assignment and analyze its structure, semi-empirical and ab initio quantum chemical calculations have been performed. It is found that, on the basis of the ordering of the states and the magnitude of their transition moments, all calculations favour a ππ* (2B2 → 2A2) rather than the earlier proposed nπ* assignment for this band. Of the methods used, only the (ab initio) CASSCF method is found to be able to simulate the observed vibrational structure adequately. This simulation is based on optimized structures and vibrational force fiel...

Journal ArticleDOI
TL;DR: In this article, various preparative procedures described in the literature for ReOCl3(PPh3)2 were repeated, and the standard methods were found to yield a yellow triclinic material (a = 11.793, bǫ= ǫ 14.300, cǫ 6.04°, βǫ 0.064), which correspond to "isomers" 1 and 2 described by Johnson, Lock, and Wilkinson in 1964.
Abstract: The various preparative procedures described in the literature for ReOCl3(PPh3)2 were repeated. The standard methods were found to yield a yellow triclinic material ( a = 11.793, b = 14.300, c = 16.422 A, α = 64.04°, β = 84.31°, γ = 87.32°, R = 0.064). The unit cell contains three discrete monomeric molecules with the trans-bis(phosphine) configuration, one of which has its Cl-Re=O unit disordered over two opposite directions. Recrystallization in CH2Cl2 yielded crystals of the bright green monoclinic polymorph (C2/c, a = 24.347, b = 9.604, c = 15.666 A, β = 116.77°, R = 0.025) containing the same monomeric molecule, but with a different conformation of the PPh3 ligands and a different packing pattern. These two polymorphs actually correspond to "isomers" 1 and 2 described by Johnson, Lock, and Wilkinson in 1964. Attempts to prepare their third "isomer" yielded powders containing ReOCl3(PPh3)2 (green polymorph) and ReNCl2(PPh3)2. The IR and 31P NMR spectra of these samples are discussed.

Journal ArticleDOI
TL;DR: In this article, a thermodynamic study of three hydroxybenzoic acids was carried out by combustion and sublimation calorimetry, heat capacity measurements, and differential thermal analysis.
Abstract: A thermodynamic study of the three hydroxybenzoic acids was carried out by combustion and sublimation calorimetry, heat capacity measurements, and differential thermal analysis. The experimental results (in kJ mol−1) are summarized as:From these experimental results, it was possible to determine for the three isomers (i) the resonance energies. From their comparison, the ortho isomer seems to be the most stable. This result is discussed using a structural consideration; (ii) the enthalpies of atomization. These values are in good agreement with that calculated using a contribution method.

Journal ArticleDOI
TL;DR: In this paper, five species of phthalocyanine-modified silica gels were prepared and the loadings of PHTHC on these gels are determined by acidic hydrolysis.
Abstract: Five species of phthalocyanine-modified silica gels were prepared. The loadings of phthalocyanine on these silica gels were determined by acidic hydrolysis. The concept of using the aggregation phe...

Journal ArticleDOI
TL;DR: Fusarium lateritium Nees is a natural antagonist of the plant pathogen Eutypa armeniacae and the bioactive metabolites of Fusarium Nees are shown to be chemically mediated.
Abstract: Fusarium lateritium Nees is a natural antagonist of the plant pathogen Eutypa armeniacae. In an effort to show that this biological phenomenon is chemically mediated, the bioactive metabolites of F...

Journal ArticleDOI
TL;DR: The spectral and electrochemical properties of tetrabenzo[5,10,15]triazaporphine (TBTAP) and its magnesium derivatives having a long alkyl chain attached to the meso carbon have been studied as discussed by the authors.
Abstract: The spectral and electrochemical properties of tetrabenzo[5,10,15]triazaporphine (TBTAP) and its magnesium derivatives having a long alkyl chain attached to the meso carbon have been studied. Both ...

Journal ArticleDOI
TL;DR: In this article, the correlation between the thermal electron mobility, μe, the radiation-induced free-ion yield Gfi at zero applied electric field, and the most probable thermalization distance b of secondary elec...
Abstract: The correlation between the thermal electron mobility, μe, the radiation-induced free-ion yield Gfi at zero applied electric field, and the most probable thermalization distance b of secondary elec...

Journal ArticleDOI
TL;DR: In this article, new preparative routes to the title compounds are reported in which the yields are substantially improved over previous methods, such as reaction of O2 with a mixture of XC6H4CN2S2+Cl− and P...
Abstract: New preparative routes to the title compounds are reported in which the yields are substantially improved over previous methods. In one method, reaction of O2 with a mixture of XC6H4CN2S2+Cl− and P...

Journal ArticleDOI
TL;DR: The dissociation constants of piperidine, 1-piperidineethanol, N-methylmorpholine, 4-(2-hydroxyethyl)morpholine (4-EML), and tropine have been determined at 15.0, 25.0 and 35.0 as discussed by the authors.
Abstract: The dissociation constants of piperidine (PD), 1-piperidineethanol (1–PE), N-methylmorpholine (MML), 4-(2-hydroxyethyl)morpholine (4-EML), and tropine (TP) have been determined at 15.0, 25.0, 35.0,...

Journal ArticleDOI
TL;DR: In this paper, general criteria for the prediction of thermodynamically stable diatomic dications (i.e., cations of + 2 charge) were discussed for a diatomic AB2+ ion.
Abstract: General criteria are discussed for the prediction of thermodynamically stable diatomic dications (i.e., cations of + 2 charge). For a diatomic AB2+, the most useful quantity for this purpose is Δ, the difference in energy between the attractive channel with asymptote A + B2+ and the repulsive channel with asymptote A+ and B+. Excluding noble gas compounds and using this measure, diatomic dications that may be thermodynamically stable include BeF2+, MgO2+, MgF2+, MgCl2+, and SiF2+, as well as several other less likely combinations. The dication BeF2+ was selected for further analysis. Ab initio calculations show that the X2Π state of this ion is thermodynamically stable by 1.08 eV and undergoes an avoided crossing that causes the effective dissociation energy to be 2.07 eV. The excited state A2∑+ is also very low-lying and predicted to be long-lived. The X2Π–A2∑+ band system is electric dipole allowed but very weak in intensity. Possible mechanisms of formation of BeF2+ are discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the energy of rotation about the C-N bond in formamide at both the molecular and atomic levels using the HF/6-31G++/HF/6 -31G¼ level of theory.
Abstract: We investigate the energetics of rotation about the C—N bond in formamide at the molecular and atomic levels using the HF/6-31G**//HF/6-31G** level of theory. At the molecular level, the barrier to...

Journal ArticleDOI
TL;DR: In this paper, the anti-selective synthesis of simple epoxides can be achieved by Sharpless epoxidation of alkenylsilanols followed by protodesilylation of the chiral epoxysilanols.
Abstract: Enantioselective synthesis of simple epoxides can be achieved by Sharpless epoxidation of alkenylsilanols followed by protodesilylation of the chiral epoxysilanols. The approach has been applied to the synthesis of frontalin.

Journal ArticleDOI
TL;DR: Chiral oxime ethers are readily prepared from chiral alkoxyamines derived from ephedrine and norephedrine as discussed by the authors, and they undergo 1,2-nucleophilic adaption.
Abstract: Chiral oxime ethers are readily prepared from chiral alkoxyamines derived from ephedrine and norephedrine. These chiral oxime ethers of isobutyraldehyde and benzaldehyde undergo 1,2-nucleophilic ad...

Journal ArticleDOI
TL;DR: Three minor indole alkaloids have been isolated from "hairy roots" of Rauwolfia serpentina Benth: 3-epi-α-yohimbine (1), 18β-hydroxy-3-epI-α -yohimine (2), and 12hydroxyajmaline (3) as mentioned in this paper.
Abstract: Three minor indole alkaloids have been isolated from "hairy roots" of Rauwolfia serpentina Benth.: 3-epi-α-yohimbine (1), 18β-hydroxy-3-epi-α-yohimbine (2), and 12-hydroxyajmaline (3). The latter compound (3) is a novel alkaloid. The alkaloid structures have been determined by spectroscopic data.

Journal ArticleDOI
TL;DR: In this paper, the effects of a weak l-type resonance between the l 0 and l 2 2 components of the vibrational level were observed in both electronic states and the off-diagonal matrix elements were evaluated in a case (b) basis.
Abstract: The (0200)Σ+ ← (000)Σ+, (0220)Δ ← (010)Π, (0200)Σ+ ← (010)Π, and (010)Π ← (000)Σ+ bands in the electronic system of SrOH have been recorded at Doppler limited resolution using CW dye laser excitation with selective detection. Fluorescence from selected rotational levels of the and vibronic states has been dispersed, providing access to the (0200)Σ+ and (0220)Δ levels of the ground electronic state. Over 1200 line positions from all transitions were included in a global least-squares fit. The effects of a weak l-type resonance between the l = 0 and l = 2 components of the ν2 = 2 vibrational level were observed in both electronic states and the off-diagonal matrix elements were evaluated in a case (b) basis. A previous analysis of the level that attributes the anomalous l-type doubling to an electronic perturbation arising from the polyad is inconsistent with our experimental results.

Journal ArticleDOI
TL;DR: In this paper, the authors derived exact analytical expressions for the initial values Φn(r0) and at an arbitrary "origin" r0, the determination of any function Φ n(r) becoming as easy as that of Φ r when e 0 is known.
Abstract: The determination of the centrifugal distortion constants (CDC) of a diatomic molecule is sought for high orders. When the vibrational energy e0 = Ev is known for a vibrational level v, the use of Rayleigh–Schrodinger perturbation theory gives the rotational constant and the CDC, where Φn(r) is the solution of the nth rotational Schrodinger equation. The problem of the determination of a function Φn is solved by deriving exact analytical expressions for the initial values Φn(r0) and at an arbitrary "origin" r0, the determination of any Φn(r) becoming as easy as that of Φn(r) when e0 is known; that of en becomes as easy as that of The application of the present formulation to the model Lennard–Jones potential function allows the numerical computation of Dv, Hv, Lv, Mv, Nv, Ov, Pv, Qv for low and high v; the CDC beyond Mv are given for the first time; higher order CDC may be reached. The results for the four lowest order constants are in good agreement with those from previously confirmed methods. Appropria...