摘要:

AbstractWith the aid of the diaphragm cell technique tracer diffusion of tritium‐labelled water in H2O—D2O mixtures has been measured at 8, 25 and 45°C. In addition, self‐diffusion coefficients in H2O—D2O mixtures have been determined by the proton n.m.r. spin‐echo technique. Paralleling the behaviour of the mutual diffusion coefficient, the tracer diffusion coefficients exhibit small negative departures from a linear concentration dependence which usually is predicted for diffusion in ide

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880112

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractA novel technique is described for the simultaneous in situ measurement of ESR and optical transients from intermediates produced by intermittent photolysis in solution. The technique has been applied to the photoreduction (λ ca. 300 ± 30 nm) of 4‐acetylpyridine (AP) in propanol(‐2) at room temperature. The measurements gave the absorption spectrum and the molar extinction coefficients of the intermediate 1‐hydro‐4‐acetylpyridinyl radical (·APH) in the 300 — 550 nm range as well as the ratio of the quantum yields for formation of · APH and disappearance of AP. Absolute values of the quantum yields at 300 nm have been determined by additional ESR and spectrophotometric measurements under steadystate conditions. The various results are discussed in terms of a mechanism proposed for the photoreduction of AP

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880113

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractReactions of OH radicals with aromatics were investigated in the presence of He at pressures ranging from 5 to 800 mbar using pulsed vacuum uv photolysis of H2O for the production of OH and time resolved resonance fluorescence for the detection of OH. At room temperature (296 K) in the presence of 133 mbar He the rate constants,k, were observed to be in the high pressure limit. The rate constants, (k± Δk)/10−12cm3s−1, were determined to be: (1.0 ± 0.2) for benzene; (120 ± 24) for aniline; (28 ± 6) for phenol, (0.50 ± 0.10) for 1,2,4‐trichlorobenzene. — For the temperature dependence of the rate constant for 1,2,4‐trichlorobenzene the Arrhenius expression (k± 3σ) = (2.3 ± 1) · 10−12exp [ — (430 ± 125) K/T] cm3s−1is obtained from measurements at 273 to 368 K. — The rate constants at room temperature can be correlated with the ionization potential,I, of the aromatics, yielding the equation: logk/cm3s−1= 0.74–1.36 ·I/eV. This equation is seen to represent the rate data on 18 aromatics to within a precision of a factor of two; with some precautions it might be used to predict rate constants for further substituted benzene aromatics. Outliers in such a diagram are benzaldehyde and the cresols (being more reactive than predicted), and diphenyl and chlorinate

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880114

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe decomposition of 1‐phenylethyl‐hydroperoxide assisted by 1‐phenyl‐ethanol has been investigated in the presence of 2,6‐di‐tert‐butyl‐4‐methyl‐phenol (ionol). Ethylbenzene was used as solvent, the temperature range was 115–130°C. The inhibition period was measured as a function of alcohol concentration (and inhibitor concentration as well). The activation parameters of hydroperoxide decomposition assisted by alcohol have been determined:kHROOH + HROH= 1.13 · 107e

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880115

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe core and valence levels for FeI2have been determined using XPS, UPS and electron impact techniques. The gaseous fragmentation products of FeI2have also been studied. By combining the present data with available published data, thermodynamic cycles are constructed for gaseous neutral species, ionic gas‐phase species and molecular iodine adsorption on iron in an attempt to systematically characterize iodine interaction with iron. Comparisons with the other ferrous halides are also draw

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880116

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractAfter electron pulse irradiation of n‐heptane, 3‐methylheptane, n‐decane, n‐dodecane, n‐tetradecane, and n‐hexadecane containing CCl4as electron scavenger, transient optical absorption bands were observed with peak wavelengths between 550 and 880 nm. The bands are assigned to the corresponding alkane radical cations. For n‐heptane radical cations a maximum extinction coefficient of 8.8 · 103dm3mol−1cm−1is estimated. Alkene radical cations were also identified in neat alkane solutions. They seem to be generated by fragmentation of vibronically excited alkane radical cations and exhibit strong optical absorption bands (π‐π*‐transitions) around 280 nm. — The kinetics of the electron transfer from n‐hexadecane as solute to cationic transients present in n‐heptane after irradiation was experimentally studied and compared with calculations using the phenomenological model of ion pair recombination presented by Infelta and Rzad [1]. From two alternative reaction mechanisms applied, differing mainly in that one assumes short‐lived mobile holes, it is concluded that positive mobile holes should also exist in n‐heptane at times<10−9s. Then they should be transformed into massive n‐heptane radical cations. — Electron transfer efficiencies were determined in n‐heptane for 11 solutes such as alkanes, alkenes and aromatics. These efficiencies are related to rate constants of the electron transfer from the solutes to mobile positive holes. The observed dependence of the rate constants on the free energy ΔGof the electron transfer reaction is explained in terms of changes in th

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880117

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880118

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880119

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880121

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880125

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY