Showing papers in "Canadian Journal of Chemistry in 1976"
TL;DR: In this paper, the rate constants for a number of exothermic displacement (SN2) reactions of the type X− + CH3Y → Y−∆+∆ + Ch3X were measured in the gas phase at 297 ± 2 K using the flowing afterglow technique.
Abstract: The rate constants for a number of exothermic displacement (SN2) reactions of the type X− + CH3Y → Y− + CH3X where X− = H−, O−, C−, F−, S−, Cl−, OH−, C2−, CN−, SH−, S2−, C2H−, NH2−, NO2−, CHF−, CH2Cl−, CH2Br−, CH3O−, CH3S−, and CH3NH− and Y = F, Cl, and Br, have been measured in the gas phase at 297 ± 2 K using the flowing after-glow technique. These gas-phase measurements provided an opportunity to determine the intrinsic nucleophilic reactivity of 'nude' anions and hence to assess the role of solvation in the kinetics of SN2 reactions proceeding in solution. Comparisons of the experimental rate constants with rate constants calculated using classical theories of capture indicate that several displacement reactions may possess large intrinsic energies of activation, . Correlations were found between apparent activation energies and the heats of reaction. These correlations provided a convenient classification of the various anion nucleophiles. Displacement was observed to compete with proton transfer in ...
180 citations
TL;DR: In this article, the density and specific heat of dilute aqueous solutions of various alcohols and polyols have been measured at 25 °C, for the following solutes: methanol, e.g.
Abstract: The density and specific heat of dilute aqueous solutions of various alcohols and polyols have been measured at 25 °C. Such measurements have been carried out for the following solutes: methanol, e...
170 citations
TL;DR: In this article, the interaction of metal-organic complexes with humic and tannic acids was studied to evaluate the possibility of metal speciation using a combination of dialysis/atomic absorption spectroscopy, and the pH characteristics of the metalorganic species.
Abstract: The interactions of Cu(II), Pb(II), Cd(II), and Zn(II) with humic and tannic acids were studied to evaluate the possibility of metal speciation using a combination of dialysis/atomic absorption spectroscopy, and the pH characteristics of the metal–organic species. The stability constants of metal–organic complexes were found to decrease in the order Pb(II) > Cu(II) > Cd(II) > Zn(II) and EDTA > humic acid > tannic acid. Scatchard plots for the metal–humic acid systems indicated two types of binding sites with a difference in stability constants of about 10. Ultrafiltration of metal–humic acid solutions indicated that the metal ions were concentrated in the large molecular size fractions (> 3.1 nm). Separation by dialysis was used to investigate the release of metal from model sediment components by the organic acids (the metal–organic complexes were non-dialyzable). For release of copper from bentonite, it was found that the amount of copper released depended on both the concentration of ligand and the sta...
160 citations
TL;DR: The crystal structures of a number of copper selenides have been re-examined using X-ray powder diffraction intensity data as mentioned in this paper, and the |F0| values for Cu1•8Se at room temperature (a = 5.765 A) are satisfied.
Abstract: The crystal structures of a number of copper selenides have been re-examined using X-ray powder diffraction intensity data. |F0| values for Cu1•8Se at room temperature (a = 5.765 A) are satisfied b...
155 citations
TL;DR: Glycylglycyl-L-histidine-N-methyl amide is a copper-binding tripeptide designed and synthesized to mimic the copper-transport site of human albumin this paper.
Abstract: Glycylglycyl-L-histidine-N-methyl amide is a copper-binding tripeptide designed and synthesized to mimic the copper-transport site of human albumin. Reddish-purple crystals of the copper-tripeptide amide complex (Cu–GGHa), grown at physiological pH, are triclinic, with cell dimensions a = 9.990, b = 9.986, c = 7.682 A, α = 107.40, β = 91.72, γ = 96.49°, space group P1, Z = two units of Cu–GGHa and two water molecules per cell. The structure was solved by interpretation of a Cu–phased Fourier map containing a great deal of false symmetry, after multiple attempts with direct phasing methods failed. Refinement proceeded to R = 0.036. The conformations of the two Cu–GGHa units are virtually identical. Each copper is tetradentate chelated by the amino terminal nitrogen, the next two peptide nitrogens, and a histidyl nitrogen of a single tripeptide molecule in a mildly distorted square planar arrangement. The Cu…N distances range between 1.90–2.05 A, with N…Cu…N angles of 165 and 176°. An oxygen atom provides a...
146 citations
TL;DR: In this paper, a sonolysis of water at 447 kHz causes a decrease in the pH and the products formed depend to some extent on the nature of the dissolved gases; products observed are hydrogen peroxide, nitrous and nitri...
Abstract: Sonolysis of water at 447 kHz causes a decrease in the pH. The products formed depend to some extent on the nature of the dissolved gases; products observed are hydrogen peroxide, nitrous and nitri...
139 citations
TL;DR: Lead(II) halides (PbX2 where X = Cl, Br, and I) formed five types of adducts with monodentate (L) and bidentate (LL) ligands as discussed by the authors.
Abstract: Lead(II) halides (PbX2 where X = Cl, Br, and I) formed five types of adducts with monodentate (L) and bidentate (LL) ligands: PbX2•L, PbX2•2L, 2PbX2•L, PbX2•LL, and PbX2•2LL, but not all halides an...
131 citations
TL;DR: A 2% cross-linked divinylbenzene-styrene copolymer was directly lithiated with n-butyllithium in the presence of N,N,N′,N −tetramethylethylenediamine.
Abstract: A 2% cross-linked divinylbenzene–styrene copolymer was directly lithiated with n-butyllithium in the presence of N,N,N′,N′-tetramethylethylenediamine The lithiated polymer on reaction with a benzophenone gave an insoluble polymer-bound trityl alcohol Further reaction with acetyl chloride gave a polymer-bound trityl chloride which, on treatment with the primary symmetrical diols 1,10-decanediol, 1,7-heptanediol, and 1,4-butanediol, gave mostly symmetrical diols monoblocked by insoluble polymer-bound trityl groups Acetylation followed by acid cleavage from the polymer gave the monoacetates of 1,10-decanediol, 1,7-heptanediol, and 1,4-butanediol and some recovered diols The recovered polymer can be efficiently recycled The quantity of recovered diol was related to the problem of 'double-binding' of the symmetrical diols to the polymer-bound trityl groups The extent of 'double-binding' could be greatly reduced by the use of polymer-bound trityl chloride prepared via the lithiated polymer and methyl benz
118 citations
TL;DR: In this paper, it was shown that β-, γ-, and δ substituent effects on 13C chemical shifts may be better understood by assuming that the upfield shifts caused by gauche γ-substituents are not due to non-bonded inte...
Abstract: It is shown that β-, γ-, and δ-substituent effects on 13C chemical shifts may be better understood by assuming that the upfield shifts caused by gauche γ-substituents are not due to non-bonded inte...
100 citations
TL;DR: The structure 1 (2-methoxy-3-bis(hydroxymethyl)methylamino-5-hydroxy-5 -hexymethyl-2-cyclohexen-1-one has been attributed to mycosporine (P. 310), a product isolated from Stereumhirsutum (Willd. ex Fr.) Fr., this result was derived from the uv, ir, ms, and nmr of 1H and 13C spectral analysis of the natural product and its derivatives as mentioned in this paper.
Abstract: The structure 1 (2-methoxy-3-bis(hydroxymethyl)methylamino-5-hydroxy-5-hydroxymethyl-2-cyclohexen-1-one has been attributed to mycosporine (P. 310), a product isolated from Stereumhirsutum (Willd. ex Fr.) Fr.; this result is derived from the uv, ir, ms, and nmr of 1H and 13C spectral analysis of the natural product and its derivatives.
95 citations
TL;DR: In this article, a study of the redox potentials of a range of metal phthalocyanines in non-aqueous media compared with analogous data for some porphyrin complexes was conducted.
Abstract: A study of the redox potentials of a range of metal phthalocyanines in non-aqueous media compared with analogous data for some porphyrin complexes provides evidence for extensive back donation in metallophthalocyanines. The potentials for some couples are exceedingly sensitive to axial ligation. It is suggested that this sensitivity may be used to 'tune' a redox couple for a specific purpose such as designing a reversible oxygen breathing system.
TL;DR: In this article, it was shown that esolv, H•, and OH formed by the radiolysis of water by 3 MeV electrons are trapped by nitroso and nitrone compounds to give nitroxides with well defined esr spectra.
Abstract: It is shown that esolv, H•, and OH formed by the radiolysis of water by 3 MeV electrons are trapped by nitroso and nitrone compounds to give nitroxides with well defined esr spectra. Three spin trapping agents were used, nitroso-t-butane, phenyl-t-butyl nitrone, and 5,5′-dimethyl pyrroline-1-oxide. The latter was shown to be an excellent compound for these studies. Complications due to the instability of some of the nitroxides were overcome by coupling the electron accelerator to the esr spectrometer to permit direct observation of the spectra.
TL;DR: Methyl iodide and potassium bicarbonate in methanol is presented as a mild, efficient, and selective reagent for the quaternization of amino groups as mentioned in this paper.
Abstract: Methyl iodide and potassium bicarbonate in methanol is presented as a mild, efficient, and selective reagent for the quaternization of amino groups. It does not attack hydroxyl groups. Its use with...
TL;DR: The charge transfer complexes of 2,2′-bithienyl, 5,5′-dimethyl-2,2''bithiamyl, and some thiophene derivatives as donors with tetracyanoethylene as an acceptor have been studied spectrophotometrical.
Abstract: The charge transfer complexes of 2,2′-bithienyl, 5,5′-dimethyl-2,2′-bithienyl, and some thiophene derivatives as donors with tetracyanoethylene as an acceptor have been studied spectrophotometrical...
TL;DR: The densities and heat capacities per unit volume of the symmetrical tetraalkylammonium bromides (R4NBr) were measured in H2O, D2O and 3 m aqueous urea from 0.01 to 1 mol kg−1 and from 5 to 55 °C.
Abstract: The densities and heat capacities per unit volume of the symmetrical tetraalkylammonium bromides (R4NBr) were measured in H2O, D2O, and 3 m aqueous urea from 0.01 to 1 mol kg−1 and from 5 to 55 °C ...
TL;DR: The photomultipliers used in single photon counting fluorescence lifetime systems have a time response function which varies with wavelength as mentioned in this paper, which results in a reduced confidence in the k...
Abstract: The photomultipliers used in single photon counting fluorescence lifetime Systems have a time response function which varies with wavelength. This variation results in a reduced confidence in the k...
TL;DR: In this paper, a series of 2-and 4-pyrones and pyridones, and their sulfur-containing analogues, were analyzed using 13.13C nmr data.
Abstract: 13C nmr data have been obtained for a series of 2- and 4-pyrones and pyridones, and their sulfur-containing analogues. Correlations have been observed between the nature of the ring hetero-atom and the chemical shift difference (Δδ) for the Cα and Cβ carbons in these conjugated systems. No significant correlation, however, appears to exist between the chemical shifts of the C=O and C=S groups. Substituent chemical shift (s.c.s.) effects for various simple substituents are compared with those in related series of compounds.
TL;DR: In this article, trityl chloride polymers were used to block one primary alcohol functional group of several polyhydroxy alcohols, and the ether linkage between the polymer and the protected alcohol was cleaved in acidic medium.
Abstract: Insoluble polymers containing trityl chloride residues were used to block one primary alcohol functional group of several polyhydroxy alcohols. After protecting the remaining hydroxyl groups by benzoylation, the ether linkage between the polymer and the protected alcohol was cleaved in acidic medium. Depending on the reaction conditions and the nature of the starting alcohol, several alcohols or bromides in which only one of the two primary hydroxyls had been esterified, were obtained. In some cases benzoyl migrations were observed. The trityl chloride polymers could be regenerated in one step without degradation or appreciable loss of activity.
TL;DR: 2-(o-Aminophenyl)-7-amino-6-methoxy-5,6-quinolinedione which has a substitution pattern most closely resembling streptonigrin also closely parallels the rate of scission of DNA of the latter in the presence of NADPH, which correlates with antitumor activity.
Abstract: The syntheses of a group of 2-(o-nitrophenyl)- and 2-(o-aminophenyl)-5,8-quinolinediones which are structurally related to the antitumor antibiotic streptonigrin are described. Ambiguities in the position of required nucleophilic displacements are resolved by independent synthesis. The rates of single strand cleavage of PM2 ccc-DNA (covalently-closed circular-DNA) induced by these compounds are compared, which correlates with antitumor activity. The 2-(o-nitrophenyl) derivatives give consistently more rapid DNA cleavage than the 2-(o-aminophenyl) compounds. The autoxidations of the dihydroxyquinolines are subject to selective catalysis by Cu2+ on. 2-(o-Aminophenyl)-7-amino-6-methoxy-5,6-quinolinedione which has a substitution pattern most closely resembling streptonigrin also closely parallels the rate of scission of DNA of the latter in the presence of NADPH.
TL;DR: In this article, the natural abundance 13C nuclear magnetic resonance spectra of a number of isoquinoline alkaloids and related model compounds have been recorded and a comparison of the spectra has been made.
Abstract: The natural abundance 13C nuclear magnetic resonance spectra of a number of isoquinoline alkaloids and related model compounds have been recorded. In almost all cases comparison of the spectra of t...
TL;DR: In the thermal decomposition of methane at temperatures from 880 to 1103 K, hydrogen and ethane are the only primary products as mentioned in this paper, and the rate of formation of ethane falls rapidly towards zero as the reac...
Abstract: In the thermal decomposition of methane at temperatures from 880 to 1103 K, hydrogen and ethane are the only primary products. The rate of formation of ethane falls rapidly towards zero as the reac...
TL;DR: In this paper, various arylsulfonyltetrazoles have been investigated to build the phosphotriester bond between appropriately protected oligonucleotides, and these reagents have been found to be highly effective with respect to the time of reaction and yields.
Abstract: Various arylsulfonyltetrazoles have been investigated to build the phosphotriester bond between appropriately protected oligonucleotides. These reagents have been found to be highly effective with respect to the time of reaction and yields.
TL;DR: The polarographic half-wave oxidation and reduction potentials, singlet and triplet energies of a series of (i) monocyclic aza-aromatics, (ii) polycyclic aromatics and their N-oxides, (iii) con...
Abstract: The polarographic half-wave oxidation and reduction potentials, singlet and triplet energies of a series of (i) monocyclic aza-aromatics, (ii) polycyclic aza-aromatics and their N-oxides, (iii) con...
TL;DR: In this article, the deprotonated thiazolidine-2-thione (ttz) with many transition metals have been prepared, and several possible structures have been proposed on the basis of chemical analysis.
Abstract: The complexes of deprotonated thiazolidine-2-thione (ttz) with many transition metals have been prepared. Probable structures have been proposed for the complexes on the basis of chemical analysis,...
TL;DR: In this paper, the 13C nmr spectra of a series of 50 methyl substituted norbornanols have been determined to gain further insight into the nature of stereochemical effects on the shieldings of carbons having closely neighboring substituents.
Abstract: The 13C nmr spectra of a series of 50 methyl substituted norbornanols have been determined to gain further insight into the nature of stereochemical effects on the shieldings of carbons having closely neighboring substituents. The relatively rigid norbornyl skeleton permits examination of a variety of orientations of substituents separated by three and four bonds, the γ and δ interactions, respectively. While methyl carbons close to γ substituents exhibit upfield shifts, as is well established, methyl carbons close to δ substituents are significantly deshielded. Even more striking shifts are found for the carbons bearing these closely lying groups. The penultimate carbons in a fragment having a δ interaction between terminal groups show deviations of up to +11 ppm from the shieldings predicted by simple additivity. For fragments having a corresponding γ interaction, the penultimate carbons absorb as much as −10 ppm from the values expected by additivity. These deviations have considerable potential for st...
TL;DR: In this paper, it was shown that 6-acetoxy-5,5-dimethylcyclohex-2-en-1-one is the only isolated product.
Abstract: Heating 5,5-dimethylcyclohex-2-en-1-one, 1, with manganic acetate in acetic acid yields 6-acetoxy-5,5-dimethylcyclohex-2-en-1-one, 2, as the only isolated product. Reaction of 3-methylcyclohex-2-en...
TL;DR: In this article, an asymmetric single minimum bridging proton potential (SMPP) was found in the vs band of the H bridged system and the origin of the asymmetric structure was discussed.
Abstract: The complex salts (Bz2H)+Y−, Bz = benzimidazole, Y = PF6− or BF4− have been identified in solution, and the molecularity of the fluoroborate, which has been crystallised, confirmed gravimetrically. Infrared and Raman spectra, together with those of the deuterated systems, indicate a similar structure in solution and the crystal, viz., an asymmetric single minimum bridging proton potential, in conformity with the X-ray structure, proving that the pronounced doublet observed in the vs band of the H bridged system is not due to proton tunnelling. The origin of the asymmetric structure is discussed.
TL;DR: In this article, densities and thermal pressure coefficients for the acetonitrile+water system at temperatures from 298.15 to 328.15 K are reported. And the variation of these parameters with composition and temperature is described.
Abstract: Densities and thermal pressure coefficients for the acetonitrile + water system at temperatures from 298.15 to 328.15 K are reported. These data are used to derive expansivities, energy–volume coefficients, cohesive energy densities, isothermal compressibilities, and derivatives of entropy with respect to pressure. The variation of these parameters with composition and temperature is described.
TL;DR: In this article, it was shown that the infrared decay of the infrared band extends over several orders of magnitude in time and, unlike that of the visible band, is independent of wavelength.
Abstract: Several deuterated aqueous glasses have been pulse-irradiated at 76 K. In addition to the well known visible absorption band of et−, a second intense infrared absorption band, with λmax > 3200 nm, has been found in (a) 50% by volume ethylene glycol, (b) 9.5 M LiCl, and (c) 2.5 and 4 M MgCl2 glasses. Electron scavengers decrease the intensities of both bands, but to different extents. An increase in temperature decreases the intensity of the infrared band, but not that of the visible band. These and other features lead us to conclude that the infrared band is due to shallowly trapped electrons which are distinctly different from trapped electrons which absorb in the visible region.The decay of the infrared band extends over several orders of magnitude in time and, unlike that of the visible band, is independent of wavelength. In the two chloride glasses the decay of the infrared band is accompanied by emission (λmax ≈ 410 nm) and is probably due to a spur reaction between an electron and hydroxyl radical t...
TL;DR: The high cost of nicotinamide coenzymes currently acts as a deterrent to the widespread adoption of alcohol dehydrogenases as chiral catalysts for effecting stereospecific and selective oxidoreduct as discussed by the authors.
Abstract: The high cost of nicotinamide coenzymes currently acts as a deterrent to the widespread adoption of alcohol dehydrogenases as chiral catalysts for effecting stereospecific and selective oxidoreduct