摘要:

Heat capacities between 100 and 270 K and enthalpies of fusion for H218O and tetrahydrofuran clathrate hydrate THF•16.9H218O have been determined using a heat flow calorimeter. The results are compared with the corresponding systems containing H216O. The isotope effects on heat capacities, enthalpies of fusion, and temperature of fusion have been used to calculate18O fractionation factors, a, for the solid–liquid equilibrium in water and the hydrate. For H218O, α = 1.0032 ± 0.0007 at 273.2 K and for THF•16.9H218O, α = 1.0037 ± 0.0006 at 277.3 K.

ISSN:0008-4042    

DOI:10.1139/v84-284

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A simple preparation of the title compound, its crystal structure, and nmr spectra are reported. The compound crystallizes in the space groupP21/n, witha = 8.109(2) Å,b = 16.183(4) Å,c = 11.968(4) Å, β = 93.45(2)°,V = 1567.7(7) Å−3, ρ = 1.987 g cm−3,Z = 4 (MoKα, λ = 0.71069 Å). The structure was solved by the heavy atom method and refined to the finalR = 0.0415 for 1261 "observed" reflections. The structure consists of five-membered cyclic C7H18N22+cations, iodide anions, and methylene dichloride molecules which are held loosely in the lattice.

ISSN:0008-4042    

DOI:10.1139/v84-285

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Extracts of the brown algaDictyotabinghamiaecontain three previously known and three new diterpenoids. The known compounds, pachydictyol A (1), dictyoxide (7), and the diacetal16, were identified by comparison of their spectral data with published values. The structures of the new diterpenoids, dictyol G acetate (12), dictyoxide A (13), and dictyotriol A diacetate (15), were proposed on the basis of their spectral data and the structures of acetate12and ether13were confirmed by chemical interconversion.

ISSN:0008-4042    

DOI:10.1139/v84-286

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The kinetics and equilibria of the oxidation of penicillamine by glutathione disulfide to form, in the first step, penicillamine–glutathione mixed disulfide and glutathione and, in the second step, penicillamine disulfide and glutathione have been studied over the pH range 4–9 by1H nmr. The reactive species are found to be penicillamine with its amino group protonated and its thiol group deprotonated and glutathione disulfide and penicillamine–glutathione mixed disulfide with their two amino groups protonated. The rate and equilibrium constants for the first step are much larger than those for the second step, indicating a small tendency for penicillamine to form its symmetrical disulfide by thiol/disulfide exchange reactions. This and the smaller reducing power of penicillamine as compared to glutathione are attributed to steric hindrance from the methyl groups adjacent to the sulfur. The kinetics and equilibria of the oxidation ofN-acetylpenicillamine by glutathione disulfide were studied at neutral pH. Conditional equilibrium and rate constants for the oxidation of penicillamine by glutathione disulfide at pH 7.4 are presented and discussed in terms of the metabolism of penicillamine.

ISSN:0008-4042    

DOI:10.1139/v84-287

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The complex formed between acridine orange (AO) and polycytidylic acid (poly(C)) was studied by spectrophotometry and spectrofluorometry. The complex was characterized by its stoichiometry, structure, and the thermodynamic parameters of its formation. The results are in agreement with an external aggregation of the protonated dye along the negatively charged poly(C) chain and indicate that approximately two AO molecules are bound per nucleotide unit of poly(C). The kinetics of the reaction between this complex and a Pd(II) complex was studied by the stopped-flow method. The addition of (dien)Pd(II) to the AO–poly(C) complex leads to the dissociation of the latter, due to fixation of the Pd(II) complex to the N3 site of the cytosine base of poly(C). The rate constant for the AO liberation, extrapolated at zero AO concentration, corresponds to the rate constant of Pd(II) fixation on poly(C). This indicates that AO can be used as an indicator for this reaction and allows kinetic studies at very low concentrations (≤ 5 × 10−6 M).

ISSN:0008-4042    

DOI:10.1139/v84-288

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A study of the aqueous chlorinolyses of a series of benzylic dithioacetals along with related α-chlorobenzylic sulfides is reported. These results require a modification of our previously proposed sulfohaloform reaction, so that thionium ion intermediates which have at least one alkyl group onsp2carbon follow a different pathway.

ISSN:0008-4042    

DOI:10.1139/v84-289

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Diffusion of sulfuric acid in aqueous solution has been measured by a conductimetric technique at 25 °C over the concentration range from 0.00035 to 0.2 mol dm−3. At the lower end of this range, dissociation of bisulfate to sulfate and hydrogen ions produces a sharp increase in the rate of diffusion of the sulfuric acid component. Expressions are developed to predict the concentration dependence of the diffusion coefficient in terms of the mobilities of the diffusing ions and the degree of bisulfate dissociation. The treatment includes electrophoretic corrections that are derived from Onsager–Fuoss theory for the unsymmetrical, multi-ion electrolyte. At low concentrations where theory applies the observed diffusion coefficients are lower than the predicted values.

ISSN:0008-4042    

DOI:10.1139/v84-290

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The compounds L2M (M = Zn, Cd; L = 2-[(dimethylamino)methyl]phenyl ligand) are obtained by reacting MCl2with LiL. The organometallic halides have been prepared, either by a similar route (LZnCl), or by the direct electrochemical oxidation of cadmium metal in the presence of 1-bromo-2-[(dimethylamino)methyl]benzene (LCdBr). The latter can be converted to LCdMe or LCdPh. Proton nmr spectroscopy shows that both L2Zn and L2Cd undergo rapid intramolecular bond fission and formation at the M + NMe2site. For L2Cd, studies of the Cd—C—C—H coupling show that the Cd—C6H5bond undergoes rapid homo-exchange at room temperature.

ISSN:0008-4042    

DOI:10.1139/v84-291

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The electrochemical oxidation of thorium in either nitric acid/tri-n-butyl phosphate (TBP) or dinitrogen tetroxide/ethyl acetate/acetonitrile media gives rise to non-aqueous solutions of thorium(IV) nitrate species. The only neutral adduct which could be obtained from HNO3/TBP solution was Th(NO3)4•8dmso (dmso = dimethylsulphoxide). Salts of [Th(NO3)6]2−with Et4N+, [(bpyH)3NO3]2+, and [(phenH)3NO3]2+(bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline) were also prepared by this route. Solutions in N2O4/EtOAc/CH3CN yield Th(NO3)4, and neutral adducts with dmso, bpy, phen, Ph3PO, and pyridine-N-oxide.

ISSN:0008-4042    

DOI:10.1139/v84-292

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Details of the synthesis, physical properties, and solid-state structure of [(C7H5O2)Ga(CH3)2]2are reported. Crystals of bis(tropolonatodimethylgallium) are monoclinic,a = 10.2669(9),b = 9.3237(3),c = 10.8671(10) Å, β = 112.896(4)°,Z = 2, space groupP21/n(22°C, λ = 0.70930 Å). The structure was solved by conventional heavy-atom techniques and was refined by full-matrix least-squares procedures toR = 0.034 andRw = 0.037 for 1746 reflections withI ≥ 3σ(I). The centrosymmetric binuclear dimer features five-coordinate gallium atoms having irregular trigonal bipyramidal coordination geometry and a planar four-membered Ga2O2ring. Important bond lengths (corrected for libration) are Ga—O(equatorial) = 1.972(2), Ga—O(axial) = 2.025(2) and 2.551(2) Å, and Ga—C = 1.951(4) and 1.954(4) Å.

ISSN:0008-4042    

DOI:10.1139/v84-293

出版商:NRC Research Press    

年代:1984

数据来源: NRC