Showing papers in "Canadian Journal of Chemistry in 1987"
TL;DR: In this paper, the effects of solvent polarity and hydrogen-bond formation on the conformational equilibria for a range of 2-substituted tetrahydropy was investigated.
Abstract: A novel application of 13C nuclear magnetic resonance provided the effects of solvent polarity and hydrogen-bond formation on the conformational equilibria for a range of 2-substituted tetrahydropy...
181 citations
TL;DR: The CH3NH3 4PbI6•2H2O (P21/n, a = 10.421(3) A, b
Abstract: The yellow (CH3NH3)4PbI6•2H2O(P21/n, a = 10.421(3) A, b = 11.334(2) A, c = 10.668(2) A, β = 91.73(2)°, Z = 2) contains isolated PbI64− octahedra, CH3NH3+ cations of two types and H2O molecules. The...
177 citations
TL;DR: Ferroceneophane 1c as mentioned in this paper is the product of the reaction of silicon tetrachloride with the dilithio derivative of N,N-dimethyl-α-ferrocenylethylamine.
Abstract: The novel ferroceneophane 1c, is the product of the reaction of silicon tetrachloride with the dilithio derivative of N,N-dimethyl-α-ferrocenylethylamine. Crystals of 1c are monoclinic, space group C2/c, a = 15.275(2), b = 9.0869(4), c = 22.363(2) A, β = 95.814(5)°, Z = 8, R = 0.037 for 2274 reflections. The tilt angle between the cyclopentadieneyl rings is 19.0(2)° and the bridge-head angle at silicon is 100.7(1)°. Other angles at silicon indicate some repulsive interaction with the CHMeNMe2 group. Silica rapidly reacts with 1c to give materials which have essentially the same Mossbauer spectra as the starting material. 1c reacts with methanol to give Fe(C5H3(CHMeNMe2)Si(OMe)3-1,2)(C5H5) and other products.
143 citations
TL;DR: In this article, a wide range of crystallinity and crystallite size were mercerized by treatment with sodium hydroxide and the resultant cellulose II samples showed only a narrow range of properties.
Abstract: Native cellulose samples having a wide range of crystallinity and crystallite size were mercerized by treatment with sodium hydroxide. The resultant cellulose II samples showed only a narrow range ...
121 citations
TL;DR: In this paper, the relationship between polyoxotungstophosphates related to PW12O403− and P2W21O716− anions was established, and a new compound K10P2W20O70 was synthesized and characterized by infrared and Ra...
Abstract: The relationship between all the polyoxotungstophosphates related to PW12O403− and P2W21O716− anions was established. A new compound K10P2W20O70 was synthesized and characterized by infrared and Ra...
116 citations
TL;DR: In this paper, the role of these radicals in oxidative stress in relation to the toxic properties of these minerals is discussed, using electron spin resonance and a spin trapping agent, and the quantity of hydroxyl radicals produced (in general, above 1014 mg−1 for a Canadian chrysotile) is a function of activation or passivation of the electron donor surface sites of the minerals.
Abstract: Formation of hydroxyl radicals, in relatively large quantities, by oxygen reduction due to the surface activity of asbestos in a cell-free system is demonstrated, using electron spin resonance and a spin trapping agent. The quantity of OH• produced (in general, above 1014 mg−1 for a Canadian chrysotile) is a function of activation or passivation of the electron donor surface sites of the minerals. The role of these radicals in oxidative stress in relation to the toxic properties of these minerals is discussed.
107 citations
TL;DR: In this article, three bis-indole alkaloids, topsentin-A (1), -B1 (2), and -B2 (3), have been isolated from the Mediterranean sponge Topsentiagenitrix and their structure determined by spectroscopic methods.
Abstract: Three new bis-indole alkaloids, topsentin-A (1), -B1 (2), and -B2 (3) have been isolated from the Mediterranean sponge Topsentiagenitrix and their structure determined by spectroscopic methods. The...
104 citations
TL;DR: In this paper, 2-N,9-diacetylguanine was treated with diphenyl carbamoyl chloride followed by heating with aqueous ethanol.
Abstract: Treatment of 2-N,9-diacetylguanine with diphenylcarbamoyl chloride followed by heating with aqueous ethanol gave 2-N-acetyl-6-O-diphenylcarbamoylguanine (2-acetamido-6-diphenylcarbamoyloxypurine). ...
101 citations
TL;DR: The ionization constants of the conjugate acids of two bases widely used in synthesis, 1,8-bis(dimethylamino)naphthalene (PS), and 1,4-diazabicyclo[2.2]octane (DABCO), have been obtained in Me2SO...
Abstract: The ionization constants of the conjugate acids of two bases widely used in synthesis, 1,8-bis(dimethylamino)naphthalene (PS), and 1,4-diazabicyclo[2.2.2]octane (DABCO), have been obtained in Me2SO...
100 citations
TL;DR: Further investigation of the South African tree Combretumcaffrum (Combretaceae) for murine P388 lymphocytic leukemia (PS) cell growth inhibitory substances has led to discovery of three new active active...
Abstract: Further investigation of the South African tree Combretumcaffrum (Combretaceae) for murine P388 lymphocytic leukemia (PS) cell-growth inhibitory substances has led to discovery of three new active ...
90 citations
TL;DR: Rolliniamucosa (Annonaceae), known in primitive medical practices of Indonesia and the West Indies as a treatment for tumors, has been investigated employing the seeds from a South American variety and the murine P388 lymphocytic leukemia for bioassay, finding a new bis-tetrahydrofuran designated rolliniastatin 1.
Abstract: Rolliniamucosa (Annonaceae), known in primitive medical practices of Indonesia and the West Indies as a treatment for tumors, has been investigated employing the seeds from a South American variety and the murine P388 lymphocytic leukemia (PS) for bioassay. The principal antineoplastic constituent (PS, 28% life extension, at 0.25 mg/kg and ED504.5 × 10−5 μg/mL) was found to be a new bis-tetrahydrofuran designated rolliniastatin 1. Structural elucidation of rolliniastatin 1 was accomplished by a combination of high resolution nuclear magnetic resonance (300 MHz), mass spectral, and X-ray crystal structure techniques.
TL;DR: The fungus Mortierellaisabellina can convert ethylbenzene and a number of para-substituted derivatives to the corresponding optically active 1-phenylethanols with enantiomeric excesses between 5 an...
Abstract: The fungus Mortierellaisabellina can convert ethylbenzene and a number of para-substituted derivatives to the corresponding optically active 1-phenylethanols with enantiomeric excesses between 5 an...
TL;DR: In this article, Azido-3′-deoxythymidine (AZT), an inhibitor of HIV replication, was found to improve the condition of patients suffering from AIDS (acquired immunodeficiency virus) infection.
Abstract: 3′-Azido-3′-deoxythymidine (AZT), an inhibitor of HIV (human immunodeficiency virus) replication, was recently found to improve the condition of patients suffering from AIDS (acquired immunodeficie...
TL;DR: The authors showed that benzophenone (BP), linoleic acid, and methyl linoleate partition completely into the micelles of phosphate buffer/0.10m SDS.
Abstract: Diffusion studies show that benzophenone (BP), linoleic acid, and methyl linoleate partition completely into the micelles of phosphate buffer/0.10 M SDS. Water-soluble compounds 4-sulphomethylbenzophenone, sodium salt (BP−), azobis(2-amidinopropane•HCl) (ABAP) and 2,5,7,8-tetramethyl-6-hydroxychroman-2-carboxylate (Trolox) show partial partitioning into the micelles. BP- and BP−-photosensitized oxidation of linoleic acid in 0.50 M SDS exhibited characteristics of free radical chain reactions including: (1) inhibition by phenolic antioxidants, (2) no retardation by singlet oxygen quenchers, and (3) the formation of conjugated hydroperoxides with cis,trans to trans,trans ratios of geometrical isomers typical of autoxidation. Quantitative kinetic studies of the order in substrate, RH, and the rate of chain initiation, Ri, show that the classical rate law, −d[O2]/dt = kp/2kt1/2[RH]Ri1/2 applies to BP-photoinitiated autoxidation of linoleic acid in SDS and the oxidizability (kp/2kt1/2 = 4.42 × 10−2 M−1/2 s−1/2...
TL;DR: The calculated z values were used to describe the structural variation of a set of 60 oxytocin peptide analogues for which literature data on biological measurements existed and are highly significant according to cross-valida.
Abstract: Previously derived principal property scales for the 20 coded amino acids have been extended to six noncoded amino acids, namely ornithine, norvaline, norleucine, O-methylated threonine, α-amino bu...
TL;DR: Induced by a stoichiometric excess of dichloro(diisopropoxy)-titanium, 1-trimethylsilyloxycyclohexene and (E)-nitroolefins (R) combine in CH...
Abstract: Induced by a stoichiometric excess of dichloro(diisopropoxy)-titanium, 1-trimethylsilyloxycyclohexene and (E)-nitroolefins (R—CH=CHNO2, R = C6H5, p-C6H4CH3, p-C6H4OCH3, p-C6H4CN, CH3) combine in CH...
TL;DR: Iodobenzene is the exclusive reaction product, and it is inferred that it is not formed directly from the primary photoproduct, but through in-cage recombination of phenyl cation with iodide anion, as in benzenediazonium iodide.
Abstract: Pulsed picosecond laser photolysis of the diphenyliodonium cation indicates that excitation of the allowed transition is followed by rapid (ps) deactivation to a homolytically dissociative state, presumably T1. Steady-state photolysis yields iodobenzene and biphenyl from the primary radical products. Iodobiphenyl is also observed. We infer in-cage recombination of these radical products, with intervention of a carbocationic intermediate. Laser flash photolysis of diphenyliodonium iodide in its charge transfer band yields an initial transient with a lifetime of ca. 200 ps. A strongly absorbing secondary transient is observed on the nanosecond time scale. Iodobenzene is the exclusive reaction product. We infer that it is not formed directly from the primary photoproduct, but through in-cage recombination of phenyl cation with iodide anion, as in benzenediazonium iodide.
TL;DR: In this article, the crystal structure of the solvated dimeric adduct [Cu(SC6H4CH3-o)•phen]2•CH3CN is triclinic.
Abstract: The electrochemical oxidation of anodic copper or silver (= M) into non-aqueous solutions of RSH (R = alkyl, axyl) gives MISR as insoluble materials in high yield. In the presence of 1,10-phenanthroline (= L), the products are MISR•phen for M = Cu, but not Ag. Gold resists oxidation under such conditions, and AuISR (R = n-C4H9, C6H5) was obtained in only poor yield. The crystal structure of the solvated dimeric adduct [Cu(SC6H4CH3-o)•phen]2•CH3CN is triclinic, with a = 10.682(3) A, b = 11.729(4) A, c = 15.608(5) A, α = 76.87(2)°, β = 76.35(2)°, γ = 68.07(2)°, V = 1742(1) A3, Z = 2 and space group . The structure is based on a folded Cu2S2 ring with an unusually short Cu—Cu distance of 2.613(3) A Each copper atom has CuS2N2 pseudo-tetrahedral stereochemistry, with Cu—S = 2.337 A(av) and Cu—N = 2.10 A(av).
TL;DR: The use of suitably blocked D-glucosamine derivatives possessing the N-allyloxycarbonyl protective group of the amino function represents potential new routes to 1,2-transglucosaylations as mentioned in this paper.
Abstract: The use of suitably blocked D-glucosamine derivatives possessing the N-allyloxycarbonyl protective group of the amino function represents potential new routes to 1,2-trans-glucosylations. Both 3,4,...
TL;DR: AITKEN et al. as discussed by the authors studied the structures of poly(organosilylenes), -(SiRH),,- (R = Ph, p-tolyl, n-hexyl, and benzyl) produced by catalytic dehydrogenative coupling of primary silanes.
Abstract: The structures of some poly(organosilylenes), -(SiRH),,- (R = Ph, p-tolyl, n-hexyl, and benzyl), produced by catalytic dehydrogenative coupling of primary silanes have been studied by infrared, nuclear magnetic resonance, and mass spectroscopies. These results, combined with data on molecular weights and molecular weight distributions from vapour pressure osmometry and gel permeation chromatography, lead to the conclusion that the polymers are linear and have SiH2R end groups. The polymers all have degrees of polymerization of ca. 10 and very narrow molecular weight dipersions. Some possible features of the mechanism that gives rise to this behaviour are discussed. C. AITKEN, J. F. HARROD et U. S. GILL. Can. J. Chem. 65, 1804 (1987). Faisant appel aux spectroscopies d'infrarouge, de rksonance magnCtique nuclkaire et de masse, on a ktudiC les structures de quelques poly(organosilylenes), -(SiRH),,- (R = Ph, p-tolyl, n-hexyl et benzyl), qui sont produits par un couplage dCshydrogCnant de silanes primaires.Ces resultats, cornbinis aux donnCes de poids molCculaires et de distributions des poids molkculaires obtenues par osmomCtrie de tension de vapeur et par chromatographie par permtation de gel, conduit a la conclusion que les polymkres sont linkaires et qu'ils contiennent des groupernents terminaux SiH2R. Les degrks de polymkrisation des polymeres sont tous d'environ 10 et les dispersions de leurs poids molCculaires sont tres Ctroites. On discute de quelques-unes des caractkristiques du mkcanisme qui donne lieu a ce comportement. [Traduit par la revue]
TL;DR: In this paper, the structure of poly-bis(pyrazine)bis(methanesulfonato-O)copper(II) is solved by conventional heav...
Abstract: Crystals of poly-bis(pyrazine)bis(methanesulfonato-O)copper(II) are orthorhombic, a = 8.199(1), b = 13.130(1), c = 6.913(1) A, Z = 2, space group Pnnm. The structure was solved by conventional heav...
TL;DR: Deuterium isotope effects on 15N chemical shifts have been investigated for the ammonium ion, ammonia, and aniline; 1Δ15N(2/1H) equals −293.3, −622.9, and −714.6
Abstract: Deuterium isotope effects on 15N chemical shifts have been investigated for the ammonium ion, ammonia, and aniline; 1Δ15N(2/1H) equals −293.3, −622.9, and −714.6 ppb respectively. Deviations from a...
TL;DR: In this paper, the cobalt complex promoted the hydrolysis of cAMP to adenosine in neutral water (50 °C) at 50 °C, at the expense of a slightly higher temperature.
Abstract: [Co(trien)(OH2)(OH)]Cl2 is highly efficient in catalyzing the hydrolysis of cAMP to adenosine in neutral water (6 × 10−6 M−1 s−1 at 50 °C). The cobalt complex promoted hydrolysis of cAMP is estimat...
TL;DR: In this paper, the activation energies of the non-catalytic and catalytic reaction pathways are 64.5 and 62.0 kJ/mol−1, respectively.
Abstract: The oxidation of glycine by permanganate ion in aqueous phosphate buffers is autocatalyzed by the soluble form of colloidal manganese dioxide formed as a reaction product. Both the noncatalytic and the catalytic reaction pathways are first order in permanganate, the noncatalytic pathway is also first order in glycine, whereas the catalytic pathway has a kinetic order unity for the autocatalytic agent and a non-integral order (1.31) for glycine. Both reaction pathways are accelerated by an increase in the pH of the medium, whereas an increase in the buffer concentration at constant pH results in an increase in the rate of the noncatalytic pathway and a decrease in the rate of the catalytic one. Additions of potassium chloride to the solutions have no kinetic effect on the reaction. The apparent activation energies of the noncatalytic and catalytic reaction pathways are 64.5 and 62.0 kJ mol−1, respectively. On the other hand, manganese(II), thiosulfate, and hexacyanoferrate(II) ions, as well as benzyltrieth...
TL;DR: Deoxyfluoro sugars were synthesized rapidly by the reaction of trifluoromethanesulfonyl derivatives of partially protected sugars with tris(dimethylamino)sulfonium diffluorotrimethylsilicate (TASF).
Abstract: Deoxyfluoro sugars were synthesized rapidly by the reaction of trifluoromethanesulfonyl derivatives of partially protected sugars with tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) ...
TL;DR: In this paper, the authors have made electrochemical measurements with a glass electrode that have yielded pK values at T = 1.298.15 K for MEA, triethanolamine (TEA), diisopropanolamines (DIPA), and methyld...
Abstract: We have made electrochemical measurements with a glass electrode that have yielded pK values at T = 298.15 K for monothanolamine (MEA), triethanolamine (TEA), diisopropanolamine (DIPA), and methyld...
TL;DR: In this paper, the authors show that the presence of bulky groups, including phenyls, on each side in the ketene plane sterically retards nucleophilic attack.
Abstract: The ketenes n-BuCH=C=O, PhCH=C=O, and Ph2C=C=O have been generated by flash photolysis and their reactivities toward water, including acid and base catalysis, have been measured in wholly aqueous media by ultraviolet spectrophotometry. The phenyl group electronically enhances the reactivity of ketenes relative to n-butyl toward water and hydroxide, but retards reaction with protic acids. The presence of bulky groups, including phenyls, on each side in the ketene plane sterically retards nucleophilic attack. The reactions are interpreted as involving in-plane attack by nucleophilic water or hydroxide in the neutral and base-induced reactions, and electrophilic protonation perpendicular to the ketene plane for the acid-catalyzed reaction.
TL;DR: In this article, the aggregation of mononuclear [2,9,16,23-tetra(neopentoxy)phthalocyanato]cobalt(II) and of some related binuclear cobalt (II) phthalocyanine derivatives, in o-dichlorobenzene, has been studied by electronic absorption spectroscopy.
Abstract: The aggregation of mononuclear [2,9,16,23-tetra(neopentoxy)phthalocyanato]cobalt(II) and of some related binuclear cobalt(II) phthalocyanine derivatives, in o-dichlorobenzene, has been studied by electronic absorption spectroscopy. Dimerisation constants and the calculated aggregate dimer spectra are reported.
TL;DR: In this article, the intramolecular radical cyclization of ω-bromo α,β-unsaturated esters for the synthesis of carbocyclic compounds is described.
Abstract: The intramolecular radical cyclization of ω-bromo α,β-unsaturated esters for the synthesis of carbocyclic compounds is described. The effect of carbon chain substituents, the bulk of the ester grou...
TL;DR: In this paper, the mechanism of the Claisen-Schmidt condensation, catalyzed by a series of activated barium hydroxide catalysts, is discussed and two kinds of ketones are studied: RCO-CH3 (R = Me, Et, Pri, But) and...
Abstract: The mechanism of the Claisen–Schmidt condensation, catalyzed by a series of activated barium hydroxide catalysts, is discussed. Two kinds of ketones are studied: R—CO—CH3 (R = Me, Et, Pri, But) and...