摘要:

A new series of solid solution Cd2−xSrxSb2O7(0 ≤ x ≤ 2) of the weberite type has been prepared and characterized. Examination of the weberite structure has revealed the existence of three critical metal–oxygen distances. The proposed ordering of the A ions permits the structural features of these compounds to be explained.

ISSN:0008-4042    

DOI:10.1139/v76-236

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The electric dipole moments of a number of 2-thiophenesulphonanilides have been measured in benzene solution at 25 °C. The data obtained have been analyzed by the vectorial additive method of calculation. Results of the calculations have shown that the SO2—NH group prefers thegauche-synconformation in which the N—H bond lies on the plane bisecting the OSO angle. Conformations about the Ph—N bond in the 2′- and 3′-substituted derivatives have also been determined and are discussed.

ISSN:0008-4042    

DOI:10.1139/v76-237

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Use of γ radiation as an ionizing source has been successfully applied to an epr study of adsorption sites and of adsorbed species in the case of H—Y zeolites. Adsorption sites have appeared to be mainly oxygen nuclei from the lattice. It has been observed that molecular hydrogen neutralizes paramagnetic sites while molecular oxygen gives rise to O2−-type radicals which have nearly equal unpaired spin density on the two nuclei (43 and 57%). Carbon monoxide gives rise to a species assigned to C+O which reacts very easily at 77 K with molecular oxygen to yield an O2−-type species for which the spin density distribution is not equivalent on the two oxygen nucleiThe nature and the mobility of OH•and NH2•radicals have been studied in detail. They arise from the ionization of physisorbed H2O and NH3, the better yield being obtained at a monolayer coverage. This study leads to an original approach to the study of the adsorptive properties of zeolites.

ISSN:0008-4042    

DOI:10.1139/v76-238

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The temperature dependence of the rate of alkaline solvolysis of monochloroacetate ion in water –tert-bulyl alcohol solutions has been determined. The rates of reaction were first order with respect to both the chloroacetate ion and to the total solvoxide ion concentrations. The reactivity is enhanced, first slowly, and then more rapidly, by increasing the concentration oftert-bulyl alcohol in the solvent mixtures. The rate of reaction increases with the reciprocal of the dielectric constant of the medium and the plot of logkvs. 1/Dcan best be represented by two lines intersecting at a point corresponding to 0.9 water mole fraction. The activation parameters ΔH*and ΔS* for the solvolysis reaction showed a minimum at about 0.9 water mole fraction. The significance of these results from the viewpoint of the electrostatic theory and the changing of solvent structure in such mixtures is discussed.

ISSN:0008-4042    

DOI:10.1139/v76-239

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The vapour pressures of solid and liquid NbCl5and TaCl5have been measured over the temperature range 425 to 525 K by a quartz Bourdon-type spiral pressure gauge. Enthalpies and entropies of sublimation, fusion, and evaporation as well as melting points and boiling points have been calculated. The present results are compared with those reported in the literature.

ISSN:0008-4042    

DOI:10.1139/v76-240

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The synthesis and separation of thecisandtransisomers of Fe(trans-σ-CF=CFCF3)(CO)4I is described. The two isomers are identified from the carbonyl region of the infrared spectrum.

ISSN:0008-4042    

DOI:10.1139/v76-241

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The structure of 1-hydroxy-6-methyl-8-hydroxymethylxanthone, a new xanthone isolated from the culture broth ofCyathus intermedius, has been confirmed by synthesis. Regioselective hydroxylation of the 8-methyl of 1-hydroxy-6,8-dimethylxanthone was achieved via the peroxide formed by reaction of oxygen with the photoenol, and also via bromination of the photoenol. Extraction of the mycelia ofC. intermediusyielded ergosterol andD-mannitol.

ISSN:0008-4042    

DOI:10.1139/v76-242

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The attempted formation of hex-5-enopyranosides from glycosiduronates by the action of Grignard reagents followed by dehydration affords hex-6-enopyranosides or 1,6-anhydrohexopyranoses as major products.13C nmr spectra of 6,6-di-C-substituted hexose derivatives are compared with those of a number of structurally related compounds. The formation of a hex-5-enopyranoside and the selective cleavage of its glycosidic linkage is illustrated by the synthesis and controlled hydrolysis of methyl 6-O-(6-deoxy-2,3,4-tri-O-methyl-β-L-arabino-hex-5-enopyranosyl)-2,3,4-tri-O-methyl-β-D-glucopyranoside(2).

ISSN:0008-4042    

DOI:10.1139/v76-243

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The syntheses of the oligoribonucleotides GpApGpC, GpCpUpC, and ApGpCpUpC by an improved phosphotriester method are described. These sequences are found in the double-stranded region adjacent to the dihydrouridine loop of several transfer RNAs. Of special significance is the improvement in yields that the activating agent, mesitylenesulfonyl triazolide, provides in coupling reactions involving purine residues.

ISSN:0008-4042    

DOI:10.1139/v76-244

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Attempted protonation of cyclobutane with H2SO4-tor CF3COOH-tfailed to give any open chain butyl product as evidence for the formation of protonated cyclobutane. The treatment of cyclobutane with an excess of CF3SO3H-tin a sealed tube at 75 °C for 3 days followed by hydrolysis did give rise to the four isomeric butyl alcohols containing some T-label in the butyl groups. The upper limit for this ring cleavage, probably via protonated cyclobutane, was about 1%. H–T exchange in the recovered cyclobutane was also observed.

ISSN:0008-4042    

DOI:10.1139/v76-245

出版商:NRC Research Press    

年代:1976

数据来源: NRC