摘要:

The kinetic form of the suppression of the perchlorate catalysis of the methanolysis of triphenylmethyl chloride in benzene solvent by tetra-n-butylammonium chloride has been investigated. This is consistent with a catalysis brought about by a simple perchlorate ion, suppressed by a competition between such ions and alkylammonium chloride ion-pairs for the alkyl halide ion-pair.The results are discussed in relation to the qualitatively similar special salt effects observed in acetolysis reactions by Winstein and co-workers, with particular reference to the necessity of the concept of intimate and solvent-separated ion-pairs in the interpretation of these effects.

ISSN:0008-4042    

DOI:10.1139/v70-001

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Infrared spectra were recorded of acetonitrile sorbed on highly degassed porous glass as well as on silica and B-, Al-, and Zr-impregnated porous glass and silica. Most of the acetonitrile was weakly and reversibly adsorbed, becoming hydrogen-bonded to surface hydroxyls. A small amount of the adsorbate formed weakly bound surface complexes with Al- and Zr-, but not with B-impurities.

ISSN:0008-4042    

DOI:10.1139/v70-002

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The adsorption of dimethyl ether has been studied at its boiling point on a range of silica gels by measurement of adsorption/desorption isotherms and isothermal calorimetric heats of adsorption. Data were determined on gels heat treated at 240, 500, 700, and 900 °C and also on gels impregnated with 0.274% w/w aluminum. On 240 °C gels, heats of adsorption varied from around 20 through 12 to 7 kcal/mole at θ = 0.01, 0.50, and 0.90, respectively. Hysteresis loops are analyzed and the initial adsorption trends explained by hydrogen bond formation between the ether oxygen and surface hydroxy groups. The enhanced amounts of ether adsorbed after aluminum impregnation are explained by the creation of either Brønsted acid sites on gels treated at 240 °C or Lewis acid sites on gels treated at the highest temperatures.

ISSN:0008-4042    

DOI:10.1139/v70-003

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The60Co γ-radiolysis of methyl iodide adsorbed on silica gel has been studied by examining the hydrocarbon products, which are mainly methane and ethane. These products are formed in large yields, indicating that a large fraction of the energy absorbed in the silica gel is able to cause decomposition of the methyl iodide. The “energy transfer” is thought to occur by electron or excitation transfer to the methyl iodide, leading to the production of methyl radicals.Evidence has been obtained that the silica gel takes part in the system as a chemical reactant as well as being an energy transfer medium, and that changing the nature of the surface changes the course of the reaction. This is most clearly shown in two ways. The ratio of methane to ethane decreases as the surface hydroxyl concentration decreases, and it is concluded that excited methyl radicals form methane by abstraction of hydrogen from surface hydroxyls. Experiments using methyl iodide-d3adsorbed on protiated silica gel confirm the participation of hydrogen from the silica gel, as the methane is over 85% CD3H, while the ethane is over 95% C2D6.The effect of additives such as N2O and SF6, which are known to be electron scavengers, was also studied. It was shown that methyl iodide is a much better electron scavenger than N2O and is as good an electron scavenger as SF6in this system.

ISSN:0008-4042    

DOI:10.1139/v70-004

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The mercury photosensitized decomposition of 2,5-dihydrofuran was studied in the vapor phase at 25 ± 2 °C. Major products are carbon monoxide, propene, and hydrogen, while biallyl, allene, methylacetylene, furan, 2,3-dihydrofuran, tetrahydrofuran, and small amounts of three unidentified products are also produced. The quantum yields of all products are decreased by increasing substrate pressure, indicating collisional deactivation of an excited state precursor which, at low pressures, decomposes according to the schemeThe product P is not furan and its possible identity is discussed. The free radical component of the reaction was further studied by carrying out the reaction in the presence of nitric oxide. The results are consistent with the above processes.

ISSN:0008-4042    

DOI:10.1139/v70-005

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Expressions are derived for the most probable distribution of molecular sizes in multi-chain polymers formed by the self-condensation of the monomer A—R—Xf− 1, where A and X are functional groups and X may be either A or B. It is assumed that all functional groups of the same kind are chemically equivalent and that intramolecular condensation may be neglected. For the case A—R—Bf− 1the results are identical with those of Flory, although it is shown that this is fortuitous and due to a cancellation of two errors in Flory's method. For the case R—Afthe results differ significantly from expressions derived by Flory and sources of error in previous work are discussed. In theory, the mole and weight fractions of individualx-mers vary continuously with the extent of reaction α over the entire range up to αmax = 2/f. The ratio of the weight average to the number average degree of polymerization is finite for all values of α below αmax. The critical point for the formation of infinitely large (wall-to-wall) molecules occurs, not at α = 1/(f− 1) as predicted by Flory, but at α = 2/f. The prediction of actual gel points is discussed in terms of the largest molecule which can have a physically meaningful existence at any fixed value of α.

ISSN:0008-4042    

DOI:10.1139/v70-006

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Methods of numerical differentiation for the calculation of surface charge densities and relative surface excesses from electrocapillary data are considered. Estimates of the random error in calculated derivatives are made by testing eight different differentiation methods with artificial data containing known levels of random error. The relative merits of these techniques and the number and spacing of data points needed to perform numerical differentiation precisely are discussed.

ISSN:0008-4042    

DOI:10.1139/v70-007

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Modifications to the Hitachi Perkin–Elmer 139 ultraviolet–visible spectrophotometer are described which enable absorption spectra of molten salts to be measured to 865 °C. The instrument can be readily reconverted for ambient temperature measurements. The solubilities and the limiting heats of solution of Ag2CrO4and PbCrO4in equimolar NaNO3–KNO3have been measured spectrophotometrically from 250 to 350 °C. The absorption spectrum of dilute solutions of Cr(III) in CsCl has been measured, the octahedral CrCl63−being present in solution at 700 °C.

ISSN:0008-4042    

DOI:10.1139/v70-008

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Specific details are given for double-tuning the Varian V-4333 probe for use in the following heteronuclear magnetic double resonance experiments: observe1H at 100 MHz; irradiate2H,19F, or31P; observe19F at 94 MHz; irradiate1H,2H, or31P. An inexpensive source of audiofrequency-noise is described which, in conjunction with the double-tuned probe and several commercially available components, constitutes the basis of a versatile heteronuclear-decoupler. Examples are given which illustrate the effectiveness of this decoupler. Double-tuning of the Varian V-4333 probe by introducing a second transmitter coil is also described.

ISSN:0008-4042    

DOI:10.1139/v70-009

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A waxlike substance extracted from the needles of black spruce by means of petroleum ether gives, upon saponification, capric, lauric, myristic, pentadecanoic, palmitic, stearic, oleic, linoleic, linolenic, arachidic, behenic, lignoceric acids, and one acid not identified. Acids of the C-20 to C-24 series constitute approximately 38% of the total acids. The unsaturated acids present are mostly of the C-18 series. The acids were identified by the gas–liquid chromatography (g.l.c.) of their methyl esters.The constituent acids of the waxlike substance from balsam fir needles are capric, lauric, myristic, pentadecanoic, palmitic, palmitoleic, heptadecanoic, stearic, oleic, linoleic, linolenic, arachidic, behenic, lignoceric, and about 7 more, not identified. The acids of the C-20 to C-24 series are present to the extent of ca. 20%. About 55% of the acids are of the C-18 series, which is mostly unsaturated. There are present certain unsaturated acids, ca. 5%, of the C-20 to C-22 series.10-Nonacosanol has been isolated from the unsaponifiable matter remaining after saponification of the waxlike substances from black spruce and balsam fir foliage. Its identity has been established by infrared, nuclear magnetic resonance, and mass spectrometry.

ISSN:0008-4042    

DOI:10.1139/v70-010

出版商:NRC Research Press    

年代:1970

数据来源: NRC