摘要:

Celenamides C (7) and D (8), two novel alkaloids closely related to peptide alkaloids found in higher plants, have been isolated as their penta (12) and nonacetyl (13) derivatives, respectively, from acetylated extracts of the spongeClionacelata(Grant). The structure elucidation of7and8is described.

ISSN:0008-4042    

DOI:10.1139/v80-338

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Nucleation rates from solutions of calcium sulfate dihydrate were measured at constant supersaturation but at varying cation:anion ratios. Induction times were also measured. The values of each were found to be dependent on the Ca:SO4ratio. The results of empirical modeling studies are reported. These suggest that ion pair formation has an impact on the nucleation event beyond that of ion removal.

ISSN:0008-4042    

DOI:10.1139/v80-339

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The effects of supporting materials (Al2O3, SiO2, TiO2) on the catalytic activity and selectivity of V2O5in the reduction of NOxwith ammonia are reported. The adsorbed state and the reactivity of the surface species were examined by an ir spectroscopy together with volumetric measurements, and the electronic state and the surface composition were studied by XPS.The reactivity of an adsorbed ammonia (NH4+) for NO2over the supported catalysts was in the following increasing order, TiO2 > Al2O3 > SiO2. NH4+(ad) and NO2(ad) were both reactive species in the reaction over V2O5, V2O5/Al2O3, and V2O5/TiO2. Among these catalysts, the oxidized surface of V2O5/TiO2adsorbs NO as NO2(ad), i.e. the reactive species, whereas other catalysts did not adsorb NO unless oxygen coexisted in the gas phase. In the case of V2O5/SiO2, the reaction between NH4+(ad) and NO2(ad) was very slow, while the surface oxygen was easily removed by the reduction with NH3and resupplied by the introduction of NO on the surface. This leads to the N2O formation through so-called redox mechanism. The NH4+(ad) on V2O5/SiO2showed an ir absorption band at 1435 cm−1which was much higher than those on other catalysts, and XPS measurement suggested that V2O5on SiO2is electrically isolated.

ISSN:0008-4042    

DOI:10.1139/v80-340

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Potassium superoxide was found to initiale autoxidations of fluorene, diphenylmethane, and distyrylmethane. In each case the oxidation results in the formation of ketones as primary products. Kinetics of the fluorene and diphenylmethane oxidations showed typical sigmoidal autoxidation rate profiles. External hydroperoxides did not affect the rates of these reactions, however, these were efficiently transformed to ketones in the presence of. A mechanism for these autoxidations is proposed.

ISSN:0008-4042    

DOI:10.1139/v80-341

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In aqueous solution, the α-deuterium isotope effects in the solvolyses of benzyl nitrates derivatives depend on the nature of the substituent in the benzene ring. In addition, the isotope effect for some derivatives depends on mole fraction of added acetonitrile while for others the isotope effect is insensitive to solvent composition. However, the kinetic solvent isotope effects forpara-methyl andmeta-trifluoromethyl derivatives remain unchanged when acetonitrile is added. These observations are accounted for in terms of a model which describes the solvolytic reaction as a two-stage process and contrasts the relative importance of bond-making and bond-breaking.

ISSN:0008-4042    

DOI:10.1139/v80-342

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Absolute rate constants of hydrogen and deuterium atom abstraction by OH and OD radicals fromn-C4H10,n-C4D10, H2and D2, and by OH radicals fromneo-C5H12have been measured at room temperature in the gas phase using the flash photolysis-resonance absorption technique. The rate constants in units of cm3mol−1s−1were found to be:The quoted errors are the 95% confidence limits. A kinetic isotope effect was observed when hydrogen was replaced by deuterium in the paraffin and H2, whereas there was no significant effect when OH was replaced by OD.

ISSN:0008-4042    

DOI:10.1139/v80-343

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A potentiometric titration method of measuring accurate H+concentrations is demonstrated for aluminum orthophosphate solutions. A calibration procedure has been used which permitted the glass electrode to be used as a concentration probe instead of as a quasi-activity probe. The random error "background noise" has been reduced by the use of Fortran computing for chemical calculations, data handling and sorting, and averaging by least squares poly nomial fits. The distribution of experimental errors along the sample titration curve is indicated by estimates for its various regions.

ISSN:0008-4042    

DOI:10.1139/v80-344

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Phacidin (4-methoxy-6-nonanoyl-2H-pyran-2-one-3-carboxaldehyde) is synthesized from triacetic acid lactone in four steps.

ISSN:0008-4042    

DOI:10.1139/v80-345

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The symmetrically substituted disilyl chalcogenides (MenH3−nSi)2E where E = O, S, Se, Te;n = 0 → 3, have been prepared and characterized spectroscopically and by cleavage reactions. The synthetic routes include reactions of halogenosilanes with water, mercury(II) sulfide, lithium telluride, and complex thio- and seleno-aluminates. The spectroscopic properties of the(MeH2Si)2E and (Me2HSi)2E species, which have not been reported previously, are discussed in some detail.

ISSN:0008-4042    

DOI:10.1139/v80-346

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Second order rate constants were measured at several temperatures for the basic hydrolysis and for concurrent carbonyl-oxygen exchange with solvent forN-benzyl-N-methylformamide-18O,N-benzyl-N-methyltrideutéroacetamide-18O, andN-benzyl-N-methyl-α,α-dideuteropropionamide-18O. Carbonyl-oxygen exchange with solvent is rationalized by invoking a conformational change in the tetrahedral intermediate. Energy barriers for these conformational changes are estimated to be of the order of 5.6, 8.0, 8.2 kcal/mol respectively for the above amides.

ISSN:0008-4042    

DOI:10.1139/v80-347

出版商:NRC Research Press    

年代:1980

数据来源: NRC