Showing papers in "Canadian Journal of Chemistry in 1990"
TL;DR: In this paper, the average ionization energy (AIE) was introduced and used as a guide to chemical reactivity in aromatic systems, which is rigorously defined within the framework of self-consistent-...
Abstract: The average ionization energy, , is introduced and is demonstrated to be useful as a guide to chemical reactivity in aromatic systems. is rigorously defined within the framework of self-consistent-...
342 citations
TL;DR: In this article, a single-crystal X-ray diffraction, 2H and 14N nmr, adiabatic calorimetry, and other methods have been used to investigate the CH3NH3PbX3 (X = Cl, Br, I) halides.
Abstract: Methylammonium lead(II) halides, CH3NH3PbX3 (X = Cl, Br, I), have been investigated by single-crystal X-ray diffraction, 2H and 14N nmr, adiabatic calorimetry, and other methods. The chloride (CL) ...
275 citations
TL;DR: The magnitude of a one-bond C-H coupling constant depends upon the chemical environment of the hydrogen atom and, especially, upon its stereochemical relationship to vicinal lone electron pairs as discussed by the authors.
Abstract: The magnitude of a one-bond C–H coupling constant depends upon the chemical environment of the hydrogen atom and, especially, upon its stereochemical relationship to vicinal lone electron pairs. Ho...
133 citations
TL;DR: In slightly acidic aqueous solutions, malvin essentially exists, in a stable form, as a fast equilibrating reaction between a ring structure, the hemiacetal B, and a chain structure as mentioned in this paper.
Abstract: In slightly acidic aqueous solutions, malvin essentially exists, in a stable form, as a fast equilibrating reaction between a ring structure, the hemiacetal B, and a chain structure, the cis-chalco...
123 citations
TL;DR: In this paper, the possible thione-thiol tautomerism of 2-and 4-mercaptopyridines, 4-6-dimethyl-2.2.
Abstract: The possible thione–thiol tautomerism of 2- and 4-mercaptopyridines, 2-mercaptopyrimidine, and 4,6-dimethyl-2-mercaptopyrimidine in solution is studied by means of absorption (UV–VIS) spectroscopy....
122 citations
TL;DR: The absolute rate constant for hydrogen abstraction from dilinoleoylphosphatidylcholine (DLPC) bilayers photoinitiated by benzophenone takes place by a free radical chain mechanism as mentioned in this paper.
Abstract: Autoxidation of dilinoleoylphosphatidylcholine (DLPC) bilayers photoinitiated by benzophenone takes place by a free radical chain mechanism according to product studies of the cis, trans and trans, trans-9- and -13-linoleate hydroperoxides formed and kinetic studies of the reaction order as a function of light intensity. The absolute rate constant for hydrogen abstraction from DLPC bilayers by peroxyl radicals is found to be 36.1 M−1 s−1 at 37 °C. Preliminary measurements of activities of phenolic antioxidants, α-tocopherol (α-T), 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMHC), 2,5,7,8-tetramethyl-6-hydroxychroman-2-carboxylate (Trolox), and 2,6-di-tert-butyl-4-methylphenol (BHT) by oxygen uptake studies during inhibition periods using photoinitiation gave uncorrected inhibition rate constants, Kinh, for α-T, PMHC, and Trolox several orders of magnitude lower than observed earlier in chlorobenzene. Three series of phenolic antioxidants, (a) polyalkyl-6-hydroxychromans, (b) polyalkyl-4-methoxyphenols, and (...
114 citations
TL;DR: In this paper, equilibrium acidities in DMSO were reported for nine cycloalkanones, acetone, acetophenone, and 19 of their α-substituted derivatives.
Abstract: Equilibrium acidities in DMSO are reported for nine cycloalkanones, acetone, acetophenone, and 19 of their α-substituted derivatives. Oxidation potentials in DMSO for the conjugate bases of most of...
96 citations
TL;DR: The product Lea-active oligosaccharide analogs were identified by both an enzyme-linked immunosorbent assay (ELISA) and by 1H NMR spectroscopy and the rate of transfer of sugar residues to 1 was measured using a coupled spectrophotometric assay.
Abstract: Chemical syntheses are reported for GDP-fucose (5), GDP-3-deoxy-fucose (6), and GDP-arabinose (7), the demethyl analog of 5. All three sugar nucleotides were found to act as donor substrates for an...
91 citations
TL;DR: Isodomoic acids E and F, two geometrical isomers of the neurotoxin domoic acid, have been found to occur with isodomeic acid and isodaic acid D in extracts of toxic mussels.
Abstract: Isodomoic acids E and F, two new geometrical isomers of the neurotoxin domoic acid, have been found to occur with domoic acid and isodomoic acid D in extracts of toxic mussels. The entire set of ge...
90 citations
TL;DR: A moderately high yield, high temperature synthesis of the title compound was reported in this article, where the tris[(3,5-dimethylpyrazolato-N1,N2)copper(I)] are triclinic, a
Abstract: A moderately high-yield, high temperature synthesis of the title compound is reported. Crystals of tris[(3,5-dimethylpyrazolato-N1,N2)copper(I)] are triclinic, a = 12.360(4), b = 14.637(4), c = 12....
84 citations
TL;DR: In the presence of an amine, copper(I) chloride is an effective catalyst for the cross-dehycrocoupling of silanes with alkynes as discussed by the authors.
Abstract: In the presence of an amine, copper(I) chloride is an effective catalyst for the cross-dehycrocoupling of silanes with alkynes. The reactions proceed at useful rates above 100 °C, but rates drop dr...
TL;DR: In this article, the electrocatalytic hydrogenation of phenanthrene, anthracene, and naphthalene was investigated under constant current at Raney nickel electrodes in a mixed aqueous organic medium.
Abstract: The electrocatalytic hydrogenation (ECH) of phenanthrene, anthracene, and naphthalene has been investigated under constant current at Raney nickel electrodes in a mixed aqueous organic medium. The ...
TL;DR: The new Ru(III) complex tran-[(dmso)2H]+[RuCl4(DMso) 2]− (1) (dmso = S-bonded dimethylsulfoxide) has been synthesized.
Abstract: The new Ru(III) complex tran-[(dmso)2H]+[RuCl4(dmso)2]− (1) (dmso = S-bonded dimethylsulfoxide) has been synthesized. New synthetic routes are reported for mer-RuX3(dms)3 complexes (dms = dimethyls...
TL;DR: The soil fungus Talaromycesflavus (Klocker) Stolk and Samson is an effective biological control for Verticillium wilt of eggplant (Solanummelongena L.), a disease caused by the fungus Verticailliumd... as discussed by the authors.
Abstract: The soil fungus Talaromycesflavus (Klocker) Stolk and Samson is an effective biological control for Verticillium wilt of eggplant (Solanummelongena L.), a disease caused by the fungus Verticilliumd...
TL;DR: In this article, the authors examined the influence of substituents X on the rate of attainment of equilibrium in trifluoroacetic acid (TFA) with 2′-hydroxychalcone.
Abstract: The 2′-hydroxychalcone (2-HOC6H4COCH=CHC6H4X)–flavanone equilibrium in trifluoroacetic acid (TFA) has been examined. The influence of substituents X on the rate of attainment of equilibrium shows t...
TL;DR: In this article, N-Acetylneuraminic acid (1) was prepared from the salivary gland mucins of the Chinese swiftlet by an improved procedure using acidic resin hydrolysis.
Abstract: N-Acetylneuraminic acid (1) was prepared from the salivary gland mucins of the Chinese swiftlet by an improved procedure using acidic resin hydrolysis. Compound 1 was transformed into the known ace...
TL;DR: The lectin IV of Griffoniasimplicifolia (GS4) specifically binds the terminal tetrasaccharide unit of the Lewis b human blood group determinant (Leb).
Abstract: The lectin IV of Griffoniasimplicifolia (GS4) specifically binds the terminal tetrasaccharide unit of the Lewis b human blood group determinant (Leb). The single crystal X-ray analysis of the compl...
TL;DR: The core oligosaccharides obtained from the lipopolysaccharides of Neisseriameningitidis serotypes 1 and 6 were isolated by mild acid hydrolysis, and their structures elucidated by combined chemica as discussed by the authors.
Abstract: The core oligosaccharides obtained from the lipopolysaccharides of Neisseriameningitidis serotypes 1 and 6 were isolated by mild acid hydrolysis, and their structures elucidated by combined chemica...
TL;DR: In this paper, the isolation and characterization of triterpene glycoside from the sea cucumber Cucumariafrondosa, collected from the Gulf of St. Lawrence, are described.
Abstract: The isolation and characterization of a novel triterpene glycoside from the sea cucumber Cucumariafrondosa, collected from the Gulf of St. Lawrence, are described. Physico-chemical data obtained on...
TL;DR: Iodine is an effective promoter for the carbonylation of primary and secondary amines to ureas using palladium acetate as the catalyst and a base (e.g. K2CO3) in acetonitrile as discussed by the authors.
Abstract: Iodine is an effective promoter for the carbonylation of primary and secondary amines to ureas using palladium acetate as the catalyst and a base (e.g. K2CO3) in acetonitrile (3 h at 95 °C and 2.7 ...
TL;DR: In this paper, Diphenylmethyl radicals have been generated by 266nm laser excitation of 1,1,3,3-tetraphenylacetone adsorbed on silica gel and included in NaX and Silicalite zeolites and have been studied using diffuse reflectance laser flash photolysis techniques.
Abstract: Diphenylmethyl radicals have been generated by 266 nm laser excitation of 1,1,3,3-tetraphenylacetone adsorbed on silica gel and included in NaX and Silicalite zeolites and have been studied using diffuse reflectance laser flash photolysis techniques. The spectrum for the radical shows λmax at ~335 nm in all three supports and is similar to that in solution. The radicals decay over time scales that vary from hundreds of nanoseconds to minutes and there are indications that some radicals may be decaying on shorter time scales than we can monitor. The efficiency of oxygen quenching increases in going from Silicalite to NaX to silica gel, consistent with the greater accessibility of oxygen to silica gel pores as compared to the narrow channels in Silicalite. Laser dose and ketone loading effects were also examined for the various supports. Potential applications of a kinetic treatment of the data based on dispersive reaction kinetics are also discussed as a means of dealing with the problem of decay kinetics ...
TL;DR: Spectra of caffeine in D2O solution (0.003 to 0.129 µm) were studied by Fourier-transform infrared spectroscopy as discussed by the authors, where the authors interpreted changes in the carbonyl stretching region in terms of the s...
Abstract: Spectra of caffeine in D2O solution (0.003 to 0.129 M) were studied by Fourier-transform infrared spectroscopy. Spectral changes in the carbonyl stretching region were interpreted in terms of the s...
TL;DR: The abscisic acid analogs (−)-(4R,5R)-, (+)-( 4S,5S)-, and (−]-(4S, 5R)-4(1E,3Z)-4-(4-carboxy-3-methyl-1,3-butadienyl)-4-hydroxy-3,3,5-trimethylcyclohexanones (dihydroabscisics) were synthesized from a common precursor, which was readily prepared by the fermentation of oxoisophor
Abstract: The abscisic acid analogs (−)-(4R,5R)-, (+)-(4S,5S)-, and (−)-(4S,5R)-4(1E,3Z)-4-(4-carboxy-3-methyl-1,3-butadienyl)-4-hydroxy-3,3,5-trimethylcyclohexanones (dihydroabscisic acids), and (−)-(4S,5R)-, (+)-(4R,5S)-, and (−)-(4R,5R)-4(Z)-4-hydroxy-4-(5-hydroxy-3-methylpent-3-en-1-ynyl)-3,3,5-trimethylcyclohexanones were synthesized from a common precursor, (−)-(6R)-2,2,6-trimethylcyclohexan-1,4-dione, which was readily prepared by the fermentation of oxoisophorone with bakers' yeast. Keywords: abscisic acid, dihydroabscisic acid, acetylenic analogs, optically active analogs, plant growth regulators.
TL;DR: In this paper, the visible spectra of a series of merocyanines, derivatives of 4-[(4-oxocyclohexa-2,5-dienylidene)ethylidene]-1,4-dihydropyridine, have been investigated in a number of solvents and solvent mixtures.
Abstract: The visible spectra of a series of merocyanines, derivatives of 4-[(4-oxocyclohexa-2,5-dienylidene)ethylidene]-1,4-dihydropyridine, have been investigated in a number of solvents and solvent mixtures. The effect of substituents on the solvatochromic behaviour of these compounds is described. All investigated merocyanines exhibited a strong negative solvatochromism. Inverse solvatochromism was observed in solvents of very low polarity for polar dyes, and in polar solvents for dyes containing hydrophobic substituents. This inversion of the solvatochromic behaviour is attributed to aggregation phenomena. Keywords: merocyanines, solvatochromism, betaine, aggregation.
TL;DR: In this article, asphaltenes from Cold Lake oil were separated into fractions by size exclusion chromatography to study the molecular size dependence of chemical structural characteristics, and each fraction was analyz...
Abstract: Asphaltenes from Cold Lake oil were separated into fractions by size exclusion chromatography to study the molecular size dependence of chemical structural characteristics. Each fraction was analyz...
TL;DR: In this article, substitution reactions of M3(CO)12 (M, Fe, Ru) and Ru4((μ-H)4(CO)) involving a range of ferrocenyl phosphines are described.
Abstract: Substitution reactions of M3(CO)12 (M = Fe, Ru) and Ru4((μ-H)4(CO)12 involving a range of ferrocenyl phosphines are described. Compounds isolated and characterized include Fe3(CO)11PFcPh2, Fe3(CO)10(PBuFcPh)2, Fe(CO)4L (L = PFc2Ph, PFc3), Ru3(CO)11L (L = PFc3, PFc2Ph, PFcPh2), Ru3(CO)10L2 (L = PFc2Ph, PFcPh2), and Ru(CO)4PFc3. Ru4((μ-H)4(CO)10 (L—L) and Ru3(CO)10(L—L) result from reactions with L—L = (Ph2PC5H4)2Fe. The structure of two derivatives are described. Crystals of Ru3(CO)11(PFcPh2) are triclinic, space group P-1, a = 8.576(1), b = 11.150(2), c = 9.160(3) A, α = 76.65(1), β = 80.75(1), γ = 72.02(1)°, Z = 2, final RW = 0.027 from 3144 observed reflections. Ru3(CO)10(Ph2PC5H4)2Fc, monoclinic crystals, space group C 2/c, a = 17.005(2), b = 18.411(1), c = 14.961(1) A, β = 117.112(8)°, Z = 4, final RW = 0.023 from 2395 observed reflections. Keywords: ferrocenylphosphines, ruthenium carbonyl derivatives, structures, synthesis, iron carbonyl derivatives.
TL;DR: The Western Pacific Ocean sponge Hymeniacidon sp.
Abstract: The Western Pacific Ocean sponge Hymeniacidon sp. was found to contain a cyclo-octapeptide designated hymenistatin 1 (1) active against the P388 leukemia cell line (ED50 3.5 μg/mL). Structural determination was accomplished utilizing high field NMR (400 MHz) and mass spectral techniques (FAB MS/MS) followed by chiral gas chromatographic analysis to establish the absolute configuration (all S-amino acids). Keywords: cytostatic, Hymeniacidon, hymenistatin, cyclo-octapeptide, P388 leukemia.
TL;DR: Present experience with sponges in the Axinella and Hymeniacidon genera suggests that the previously known hymenialdisine and analogous imidazole derivatives may be widely distributed among these and related orange colored Porifera.
Abstract: Western (Palau) and Eastern (State of Truk) Caroline Islands and Papua New Guinea sponges of the genera Axinella and Hymeniacidon were found to contain the cytostatic (PS ED50 2.5 and 2.0 (μg/mL) and antineoplastic (PS T/C 143 at 3.6 mg/kg and T/C 138 at 3.6 mg/kg) pyrrologuanidines 1a and 1b. The related hydantoin 2, designated axinohydantoin, was also isolated from an Axinella sp. and its structure was assigned by X-ray crystallographic techniques. Present experience with sponges in the Axinella and Hymeniacidon genera suggests that the previously known hymenialdisine (1b) and analogous imidazole derivatives may be widely distributed among these and related orange colored Porifera. Keywords: axinohydantoin, hymenialdisine, Axinella, Hymeniacidon, cystostatic.
TL;DR: In this article, Lignin residues from the alkaline hydrolysis of solvolytic lignin have been characterized by elemental analysis, size exclusion chromatography, Fourier transform infrared spectroscopy, 13C NMR, and...
Abstract: Lignin residues from the alkaline hydrolysis of solvolytic lignin have been characterized by elemental analysis, size exclusion chromatography, Fourier transform infrared spectroscopy, 13C NMR, and...
TL;DR: The 113Cd chemical shift shows a great sensitivity to the environment of Cd, even for complexes with closely related structures as mentioned in this paper, and the presence of five resonances due to Cd surrounded by CxN(4-x) (where x = 0 to 4) in Cd(CN)2 and Cd[C6H12 indicates a static disorder of the CN groups.
Abstract: 113Cd magic angle spinning NMR, with and without 1H cross-polarisation and decoupling, has been used to study a number of Hofmann-type clathrates and related compounds. The 113Cd chemical shift shows a great sensitivity to the environment of Cd, even for complexes with closely related structures. The presence of five resonances due to Cd surrounded by CxN(4–x) (where x = 0 to 4) in Cd(CN)2 and Cd(CN)2•C6H12 indicates a static disorder of the CN groups, which makes these materials orientational glasses. Keywords: 113Cd NMR, Hofmann-type clathrates, Cd(CN)2, disorder, orientational glass.