摘要:

Measurements of the yield of NO2in N2–NO mixtures give a neutral dissociative excitation yield ofin good agreement with those derived from excitation cross-section measurements and from product yield measurement in the radiolysis of N2–O2mixtures.The dependence of exchange yields in the radiolysis of28N2–30N2mixtures on pressure, O2concentration, and dose-rate has been measured. The results are consistent with a significant contribution to these yields from the isotopic exchange reaction of N+with N2. They also indicate that dose-rates of the order of >1022 eV g−1s−1are required for the N2+ions to contribute to the exchange yield.

ISSN:0008-4042    

DOI:10.1139/v78-023

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

An analysis of the theoretical correction factors for diffusion toward spherical and cylindrical electrodes has been made. The Cottrell equation is a limiting case for spherical and cylindrical diffusion and is accurate only when bothD1/2/r0andtare small.

ISSN:0008-4042    

DOI:10.1139/v78-024

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Liquid-phase reactions of alkylperoxy radicals with cupric complexes of dialkyldithiophosphoric and dialkyldithiocarbamic acids have been examined. These complexes have been shown to be extremely efficient peroxy radical scavenging antioxidants for hydrocarbon autoxidation. Initial rates of oxygen absorption by typical hydrocarbons were extremely slow implying inhibition rate constants > 106 M−1s−1. The initial rate of disappearance of the dithiocarbamate was equal to the rate of chain initiation (Ri) whereas the rate of disappearance of the dithiophosphate was twice as fast asRi. In both cases the rate of complex disappearance slowed down as the complex was consumed. Autoxidation of styrene commenced as soon as the complex disappeared while cumene did not absorb oxygen for a considerable length of time after complex destruction. Cumylperoxy radicals were converted to α-cumyl alcohol, α-methylstyrene, and acetophenone by reaction with these complexes and the copper ions were eventually precipitated as copper sulphate. In the case of the dithiocarbamate three intermediate cupric complexes were detectee by epr spectroscopy.

ISSN:0008-4042    

DOI:10.1139/v78-025

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The epr spectra of three intermediate copper(II) complexes formed by oxidation of bis[N,N-dialkyl(dithiocarbamato-S,S′)] copper(II) by alkyl hydroperoxides and alkylperoxy radicals are reported. Isotropic and anisotropic spectra of the complexes formed from alkylperoxy radicals enriched with17O are consistent with the following structures: [Cu(S2CNR2)(OS2CNR2)] (I), [Cu(OS2CNR2)2] (II), and [Cu(OS2CNR2)(O2S2CNR2)] (III). The isotropic17O hyperfine interaction of I is 19.2 G while the anisotropic spectrum of II indicates that the two oxygen nuclei are equivalent. The anisotropic17O hyperfine splitting constants are consistent with a structure for these complexes in which the S—O bond(s) is directed out of the plane of the complex and not coordinated to the copper.

ISSN:0008-4042    

DOI:10.1139/v78-026

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Autoxidation of 3-methylpentane in the presence oftert-butyl hydroperoxide gives, after reduction with triphenylphosphine, 3-methyl-3-pentanol and 3-methyl-2-pentanol as the major reaction products. The overall rate constant for reaction of (CH3)3COO·with this substrate at 30 °C is 0.008 ± 0.001 M−1s−1which consists ofk/tertiary C—H = 0.007 ± 0.001M−1s−1andk/secondary C—H = 0.0002 ± 0.0001 M−1s−1. The products from cooxidation of cumene and 3-methylpentane in the presence oftert-butyl hydroperoxide are formed in yields which are consistent with these rate constants relative to a value of 0.16 M−1s−1for cumene. The Arrhenius equations for reaction of (CH3)3COO•with thet-C—H ands-C—H of 3-methylpentane relative to the Arrhenius equation for reaction of (CH3)3COO•with cumene (log (k10/M−1s−1) = (8.7 ± 0.3) − (13.2 ± 0.4)/θ) arerespectively, where θ = 2.303RT kcal mol−1

ISSN:0008-4042    

DOI:10.1139/v78-027

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

tert-Butylperoxy radicals enriched with oxygen-17 react with phenyltert-butyl nitrone to give α-tert-butylperoxybenzyltert-butyl nitroxide withaN = 13.42 G,aH = 0.95 G,aoβ = 2.9 G,g = 2.0064. The O-hfsc decreases with an increase in temperature while the H-hfsc increases with an increase in temperature. This radical is not stable above about 273 K and is replaced by α-tert-butoxybenzyltert-butyl nitroxide,aN = 13.62 G,aH = 1.72 G,aoβ = 5.05 G,g = 2.0064.Alkylperoxy radicals are also trapped by 2-methyl-2-nitrosopropane to give alkylperoxytert-butyl nitroxideaN = 28.7 G,aoROO = 4.6 G,g = 2.0056 while the epr parameters for alkoxytert-butyl nitroxide areaN = 27.25 G,aoRO = 1.03 G,g = 2.0057.

ISSN:0008-4042    

DOI:10.1139/v78-028

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The crystal structure of µ-oxobis(cis-dichloro-cis-di(pyridine)-trans-oxorhenium(V)), ORe(C5H5N)2Cl2•O•Re(C5H5N)2Cl2O bas been studied by single crystal X-ray methods. The crystals were orthorhombic with lattice parametersa = 15.367(2),b = 10.283(2),c = 16.685(2) Å. The space group wasPna21and there were four formula weights per unit cell. A total of 3339 reflections, of which 2990 were observed, were examined, and the structure refined by full matrix least squares (treating the pyridine rings as groups) to anR2value of 0.0449. The dimer had a roughly rectilinear O—Re—O—Re—O backbone with pairs of chlorine atoms and pyridine molecules arrangedcisin each half of the dimer. The two halves of the dimer were arranged such that the pairs ofcisatoms in one half were rotated about the Re(1)–Re(2) axis almost 113 ° when compared to the corresponding pair in the other half. Important bond lengths (Re—O(terminal), 1.715(16), 1.764(16); Re—O(bridging), 1.943(16), 1.903(16); Re—Cl, 2.356(5)–2.390(5); Re—N, 2.116(16)–2.180(16)) were close to previously observed values. The molecule was markedly disturbed from the idealized structure and this was caused by intramolecular non-bonded interactions.

ISSN:0008-4042    

DOI:10.1139/v78-029

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Reaction of alicyclic-1,2-diones (2a–d) with dimethyl 3-ketoglutarate1at room temperature in aqueous buffer (pH = 5.6) provided good yields of the tetramethylpropellanedione tetracarboxylates (3a–d), respectively. Hydrolysis and decarboxylation of the β-ketoester functions, followed by Wolff–Kishner reduction of the corresponding propellanediones (4a–d) has resulted in synthesis of [10.3.3]-, [6.3.3]-, [4.3.3]-, and [3.3.3]propellanes (5a–d). The13C nmr of propellanes5a–care also reported.

ISSN:0008-4042    

DOI:10.1139/v78-030

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The flowing afterglow technique has been employed in the measurement of rate and equilibrium constants at 296 ± 2 K for unsolvated proton transfer reactions of the typeand several solvated proton transfer reactions of the typewhere X and Y may be H2O, H2S, HCN, or H2CO. Where possible, direct comparisons are made with similar measurements performed with other techniques. The equilibrium constant measurements provide a measure of the relative proton affinities of H2O, H2S, HCN, and H2CO and absolute values for PA(H2O) = 166.4 ± 2.4 kcal mol−1, PA(H2S) = 170.2 ± 1.8 kcal mol−1, and PA(HCN) = 171.0 ± 1.7 kcal mol−1when reference is made to PA(H2CO) = 170.9 ± 1.2 kcal mol−1which can be derived from available thermochemical information. The rate constant measurements reinforce the generalization that unsolvated proton transfer involving simple molecules proceeds with high efficiency and provide information about the influence of solvation on this efficiency.

ISSN:0008-4042    

DOI:10.1139/v78-031

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The reactivity of a series of cyclopropylalkenes, as well as norbornene and cyclohexene, withp-chlorobenzenesulfenyl chloride in CH2Cl2at 25 °C have been measured. Rates of reaction of several of the substrates were also measured in acetic acid and 1,1,2,2,-tetrachloroethane so that factors for converting rates from one solvent to another could be obtained. The rates of the sulfenyl halide additions varied over a total range of 193 from the least reactive alkene, ethylene, to the most reactive, 1,1-dicyclopropylethylene. This relatively small variation is in accord with all of these reactions involving bridged rate-determining transition states. The corresponding range in reactivity for acid-catalyzed hydration, a reaction involving protonation on carbon to give an open carbonium ion, is 1016. These two reactions are proposed as bases for structure–reactivity comparisons to determine whether other reactions involve bridged or open transition states.

ISSN:0008-4042    

DOI:10.1139/v78-032

出版商:NRC Research Press    

年代:1978

数据来源: NRC