摘要:

The crystal structure of benzil bisthiosemicarbazonatocopper(II) has been solved and refined to anR-value of 0.082. The dark red triclinic crystal has cell dimensionsa = 960.8(4),b = 1090.7(6),c = 895.8(4) pm, α = 106.23°(4), β = 92.36°(7), γ = 99.50°(7), and belongs to space groupwith two molecules per cell. The measured and calculated densities are 1.571 and 1.568 g cm−3, respectively, using C16H14CuN6S2(mol. wt. 417.99). The copper coordination is significantly non-planar. The five non-hydrogen atoms of each original thiosemicarbazide molecule lie close to planes set at a dihedral angle of 8.9°. The fold is away from the origin and the neighbouring molecule. Bond lengths to copper are: Cu—S(1) = 223.7(3), Cu—S(2) = 223.4(3), Cu—N(13) = 197.1(6), Cu—N(23) = 197.0(7) pm. The bond angles at the Cu atom are S(1)—Cu—S(2) = 108.62°(9), N(13)—Cu—N(23) = 81.1°(3), N(13)—Cu—S(1) = 85.1°(2), and N(23)—Cu—S(2) = 85.0°(2). The first and second phenyl rings are at 100.3° and 93.0° to the mean Cu coordination plane, which is at a perpendicular distance of 330 pm from a similar plane in the inverse molecule. Intermolecular double hydrogen bonding occurs at each side of the complex between the uncoordinated nitrogen atoms, thus linking the molecules into parallel ribbons.

ISSN:0008-4042    

DOI:10.1139/v79-098

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Dielectric constants of water + glycol (mono-, di-, tri-, and tetraethyleneglycol) mixtures have been measured at 298.15 K over the entire composition range. The mixtures involving monoethyleneglycol have also been studied at temperatures from 308.15 to 288.15 K. Calculated deviations from ideality are always positive and show one maximum. Related properties have been computed: polarizability volume and excess polarizability volume, correlation factor of mixtures, and dipole moments of both components using the Mecke–Reuter treatment. Results support conclusions previously deduced from excess and partial molar volumes; they suggest that the addition of glycol molecules gives rise to a slight enhancement of the water-lattice in the water-rich region, followed by a progressive destructuring; the ether functions do not seem to play a prominent role.

ISSN:0008-4042    

DOI:10.1139/v79-099

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Epoxidation of Δ2-1-carbacephems2followed by base treatment gave the allylic alcohols4. Oxidation of4gave the 2-keto-Δ3-carbacephem9which could be reduced to the isomeric allylic alcohol7. Conversion of these intermediates to a series of biologically active cephalosporin analogs13g–land14is described.

ISSN:0008-4042    

DOI:10.1139/v79-100

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The reactions of bromine with uracil, 1-methyluracil, 3-methyluracil, and with 1,3-dimethyluracil in 0.125–2.0 Maqueous sulfuric acid have been examined. Under these conditionsrapidattack by bromine upon the uracil leads to the formation of an observable intermediate, a 5-bromo-5,6-dihydro-6-hydroxyuracil, which subsequently undergoesslowacid-catalyzed dehydration to the appropriate 5-bromouracil. The intermediates derived from uracil and 3-methyluracil also show acid independent dehydration. The dehydration of the adduct derived from 6-methyluracil proceeds much more rapidly and so precludes observation of that adduct. The dehydrations show significant primary isotope effects for the rupture of C(5)—H bonds of the intermediates. The mechanistic implications of these results are discussed.

ISSN:0008-4042    

DOI:10.1139/v79-101

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The rigid-lattice nmr line shape of the four-proton system in 1,2-dihaloethanes has been obtained by spectral simulation as a function of dihedral angleand used to show that 1,2-dichloroethane is encaged in the structure II hydrate in agaucheconfiguration withVery broad low-temperature dielectric absorption is associated with an average activation energy of 0.87 kcal/mol for guest-molecule reorientation.

ISSN:0008-4042    

DOI:10.1139/v79-102

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The gas phase ionization potentials, electrochemical redox potentials and spectroscopic properties of a series of thiochroman-4-one and thiochromone derivatives have been studied. A dramatic shift in the energies of the lowest vacant and highest occupied molecular orbitals of the parent thiochromanone as a function of the addition of a double bond and/or oxidation of the sulphur atom was observed. This shift in energy of the molecular orbitals was reflected in their spectroscopic characteristics. The lowest singlet (and triplet) state of compounds1–3in solution is π,π* in nature, while that of compounds4–6is n,π*. These results are best explained in terms of substituent effects on the energetics of the acetophenone moiety. The change in the nature of the lowest excited state from π,π* (1–3) to n,π* (4–6) should result in quite different types of photochemistry for the two series.A linear free-energy relationship between the singlet and triplet energies and the absolute difference between the oxidation and reduction potentials of the two series was found. These correlations have been utilized to estimate the half-wave oxidation potentials of compounds3–6. A correlation was found to exist between the gas phase ionization potential and the solution electrochemical oxidation potential.

ISSN:0008-4042    

DOI:10.1139/v79-103

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Under the agency of an iodonium ion, the tertiary anomeric hydroxyl of tetraacetyl fructofuranose adds stereoselectively in a 1,4 sense, to a pyranoid 4,6-O-benzylidenated conjugated diene receptor. The resulting disaccharide, isolated in 45% yield, is an hex-2-enopyranoside possessing an allylic primary iodide which can be oxidised to an aldehyde either directly or after hydrolysis to the allylic primary alcohol. The aldehyde is decarbonylated and the unsubstituted hex-2-enopyranoside formed undergoes hydroxylation giving exclusively themanno-diol. After protecting the equatorial hydroxyl as the benzoate ester, the axial 2-hydroxyl group is inverted via oxidation followed by borohydride reduction. Acetylation gives the known 4,6-O-benzylidene hexaacetyl derivative of sucrose, which is identified by mixture melting point.

ISSN:0008-4042    

DOI:10.1139/v79-104

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Condensation of the diene1with the α,β-anomeric mixture of tetraacetyl fructofuranose and processing of the resulting product gives rise to a series of disaccharides,5,6, and7, each of which is a mixture of two substances differing only in the anomeric configuration at the fructosyl centre, the linkage at the pyranosyl moiety being α in all cases. This conclusion is reached by careful comparison of the1Hmr and13Cmr spectra of these disaccharides with those of a number of fructofuranose derivatives. There are interesting correlations in configuration, conformation, and optical rotation.

ISSN:0008-4042    

DOI:10.1139/v79-105

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Three disaccharides containing α-linked rhamnopyranoside units have been synthesised in a form suitable for covalent linkage to protein. The artificial antigens obtained in this manner represent structural elements similar to portions of the repeating unit of theShigellaflexneriO-antigen. The glycosylation reactions leading to the disaccharides utilised silver trifluoromethanesulphonate andN,N-tetramethylurea, orsym-collidine, conditions which generated the three 1,2-trans-linked glycosides in high yield and stereospecificity. The blocking groups used in these syntheses are consistent with further chain extension to tri- and tetrasaccharides.2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-glucopyranosyl chloride and the 1,2-oxazoline derivative obtained from it were not effective in glycosylating the C-2 position of partially blocked rhamnopyranoside but 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-D-glucosyl bromide gave the desired 1,2-trans-2-amino-2-deoxyglucoside in good yield. Selective conversion of the phthalimido group to an acetamido function in the presence of an ester function was achieved, thereby extending the utility of the phthalimido protecting group to sequential oligosaccharide synthesis, in which 2-acetamido-2-deoxy-β-D-glucosides are internal units. Proton nmr evidence in support of theexo-anomeric effect is presented.

ISSN:0008-4042    

DOI:10.1139/v79-106

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The proton transfer reaction between 2,4,6-trinitrotoluene and 1,1′,3,3′-tetramethylguanidine in dimethylformamide solvent shows a large primary deuterium isotope effect,kH/kD = 24.3 at 0 °C and 16.9 at 20 °C. The enthalpy of activation difference (ΔHD≠ − ΔHH≠) = 2.6 ± 0.4 kcal mol−1and the entropy of activation difference (ΔSD≠ − ΔSH≠) = 3.4 ± 1.3 cal mol−1K−1. This isotope effect, when fitted to Bell's equation, indicates that there is a considerable contribution to this reaction from tunnelling of the proton through the potential energy barrier.

ISSN:0008-4042    

DOI:10.1139/v79-107

出版商:NRC Research Press    

年代:1979

数据来源: NRC