摘要:

AbstractThe reactions of hydroxyl radicals with eight substituted aromatic hydrocarbons and four olefins were studied utilizing the flash photolysis–resonance fluorescence technique. The rate constants were measured at 298°K using either Ar or He as the diluent gas. The values of the rate constants (k× 1012) in the units of cm3/molec. sec are(a) OH +o‐xylene → products: (12.9±3.8), 20 torr He; (13.0±0.3), 20 torr Ar; (12.4±0.1), 200 torr He;(b) OH +m‐xylene → products: (15.6±1.4), 3 torr Ar; (19.4±0.8), 20 torr Ar; (21.4±0.2), 20 torr He; (20.3±1.9), 200 torr Ar; (20.6±1.3), 200 Torr He;(c) OH +p‐xylene → products: (8.8±1.2), 3 torr Ar; (10.1±1.0), 20 torr He; (10.5±0.6), 200 torr He;(d) OH + ethyl benzene → products: (7.50±0.38), 3 torr He; (7.06±0.26), 20 torr He; (7.95±0.28), 200 torr He;(e) OH +n‐propylbenzene → products: (6.40±0.36), 20 torr He; (5.86±0.16), 200 torr He;(f) OH + isopropylbenzene → products: (7.79±0.40), 200 torr He;(g) OH + hexafluorobenzene → products: (0.221±0.020), 20 torr He; (0.219±0.016) 200 torr He;(h) OH +n‐propyl pentafluorobenzene → products: (2.52±0.54), 3 torr He; (3.01±0.76), 20 torr He; (3.06±0.24), 200 torr He;(i) OH + propylene → products: (25.6±1.2), 20 torr He; (26.3±1.2), 200 torr He;(j) OH + 1‐butene → products: (29.6±1.9), 3 torr He; (29.4±1.4), 20 torr He;(k) OH +cis‐2‐butene → products: (43.2±4.1), 3 torr He; (42.6±2.5), 20 to

ISSN:0538-8066    

DOI:10.1002/kin.550100802

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe quantum efficiencies of the primary processes in formaldehyde photolysis (ϕ1and ϕ2) were determined as a function of wavelength in the range from 2890 to 3380 Å and at 25°C: CH2O +hν → H + HCO (1); CH2O +hν → H2+ CO (2). The estimates of ϕ2were derived from ΦH2values obtained in photolyses of CH2O‐isobutene mixtures at high isobutene concentrations where H‐atom scavenging was essentially complete. Values of ϕ1+ ϕ2, obtained from the ΦH2values from the pure CH2O photolyses, were very near unity at all but the longest wavelengths employed: ΦH2= ϕ1+ ϕ2= 1.02 (2930 Å); 1.12 (3130 Å); 1.06 (3150 Å); 1.01 (3250 Å); 1.0 (3335 Å); 0.75 (3380 Å). Our results showed that the onset of photodissociation of CH2O by process (1) was at 3370 ± 10 Å; this corresponds toD(H‐CHO) = 84.8 plusmn; 0.3 kcal/mol. The values of ϕ1increased regularly with decreasing wavelength from 0 at 3370 Å to ∼0.7 at 3175 Å. Little further variation in ϕ1occurred from 3175 to 2890 Å. For experiments at λ = 3300 Å, the addition of CO2(∼300 torr) reduced ϕ2, while the effect on ϕ1appeared to be small. The present results coupled with the solar irradiance estimates of Peterson [24] and the extinction data for CH2O from McQuigg and Calvert [7] were used to make new estimates of the apparent first‐order rate constants (min−;1× 103) of process (1) in the lower atmosphere at various solar zenith angles (in parentheses): 2.31 (0°); 2.17 (20°); 1.71 (40°); 0.92 (60°); and 0.17 (78°). The corresponding first‐order rate constants (min−1× 103) for solar light absorption by CH2O in the lower atmosphere are 7.

ISSN:0538-8066    

DOI:10.1002/kin.550100803

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe experimental data on alkane decomposition from shock‐tube and radical buffer studies and radical combination from very‐low‐pressure pyrolysis and modulation spectroscopy are shown to be consistent. They lead to experimentalAfactors which decrease by factors of 10–2000 from 300° to 1100°K. Heats of formation for ethyl, isopropyl, andt‐butyl radicals have been found to be 10, 10 and 20 kJ higher than currently accepted numbers from metathesi

ISSN:0538-8066    

DOI:10.1002/kin.550100804

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractCO laser emission at 5 μm was detected when SO2and CFBr3were flash photolyzed in the vacuum ultraviolet above 165 nm. Over 40 vibrational–rotational transitions ranging from Δv= 2 → 1 to 14 → 13, with the exception of those between 8 → 7 and 11 → 10, were identified. The CO emission is believed to result from the O + CF reaction:The vibrational population of the CO has been measured by means of a CO laser resonance absorption method. The CO was found to be vibrationally excited tov= 24 with a vibrational temperature of about 1.4 × 104°K. The “surprisal analysis” of the observed CO distribution showed the possible occurrence of a minor process (presumably O + CFBr) that generated vibrationally colder CO. The effects of various additives on the CO emission were also examined. The addition of CO2to a D2‐SO2‐CFBr3‐He mixture resulted in a simultaneous osciallation at 3.6, 5, and 10.6 μm due to DF, CO, and CO2, respectively. Additionally, the utilization of the O + CFn(n= 1, 2, 3) reactions as F‐atom sources for HF‐laser operation in flash‐initi

ISSN:0538-8066    

DOI:10.1002/kin.550100805

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThis investigation presents a detailed examination of the relative reliability of the comparative and absolute rate methods as they are applied to kinetic studies in the single‐pulse shock tube. For this purpose two previously studied reactions, the thermal elimination of HCl from ethyl chloride andn‐propyl chloride, were selected and mixtures of these compounds were shock heated to temperatures in the range of 960°‐1100°K. The experimental results were analyzed by both methods and the rate constants obtained from these analyses are compared with those of previous studies. The advantages and shortcomings of both methods are noted and it is concluded that reliable kinetic data can be obtained by the absolute rate (isolation technique) method with careful examination of the gas‐dynamic flow conditions and taking cognizance of the incident shock deceleration. The limitations of the comparative rate technique encountered in the present study were similar to those detailed in previous inves

ISSN:0538-8066    

DOI:10.1002/kin.550100806

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe adsorption/desorption and reactive behavior of formaldehyde was studied on clean single‐crystal Ni(110) at adsorption temperatures down to 200 °K. For low exposures of the surface to formaldehyde, hydrogen and CO binding states were populated due to decomposition of the molecule upon adsorption. Higher exposures gave rise to a decomposition‐limited hydrogen peak exhibiting an activation energy of 20 kcal/gmol and an apparent frequency factor of 1014sec−1. At initial coverages of H2CO exceeding about 0.5, monolayer methanol was observed to form. The formation of methanol involved a hydrogen atom transfer between two adsorbed H2CO molecules and did not occur totally via surface hydrogen. Self‐oxidation to form CO2was also observed. The surface exhibited reaction heterogeneity, and the surface reactivity was observed to depend on the temperature of adsorption of reactants, suggesting strong adsorbate‐induced surface “rec

ISSN:0538-8066    

DOI:10.1002/kin.550100807

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe oxidative cleavage of some aliphatic ketoximes by thallium(III) acetate was studied in the temperature range of 20–40°C. The reactions were followed by determination of the rates of disappearance of thallium(III) acetate for variations in [substrate], [Tl(III)], [H+], ionic strength, temperature, etc. The reactions were found to be totally second order–first order with respect to each reactant. The second‐order rate constants and thermodynamic parameters were evaluated and discussed. The mechanism proposed involves one‐electron oxidation to the iminoxy radical followed by an another one‐electron oxidation to the hydroxynitroso compound which dimerizes and decomposes to give the carbonyl compounds and hyponi

ISSN:0538-8066    

DOI:10.1002/kin.550100808

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550100809

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe rate of disappearance of C2N2in the presence of a large excess of H atoms has been measured in a discharge‐flow system at pressures near 1 torr and temperatures in the range of 282–338 K. Under these conditions the reaction has a small negative temperature coefficient. A transition from second‐order to third‐order kinetics with decreasing pressure occurs at pressures near 1 torr. The results are discussed in terms of the mechanismwherek7= (1.5 ± 0.2) × 10–15cm3/molec1·sec is found for the forward rate of reaction (7). The results also givek7k8/k−7= 3.7 × 10−31cm6/molec2·sec andk7k9/k−7= 3.0 × 10−32cm6/molec2·sec, the first being probably an upper limit and the second probably a lower limit; hencek8/k9= 12 is

ISSN:0538-8066    

DOI:10.1002/kin.550100810

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe kinetics of gamma‐radiation‐induced free‐radical chain reactions in solutions of carbon tetrachloride in mixtures of varying composition of cyclohexane andn‐hexane was investigated in the temperature range of 296°–413°K. Trichloromethyl radicals were produced by the reaction of radiolytically generated alkyl radicals with the solute. The kinetics of the following reactions were studied:The following rate expression was obtained:\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_4 /k_5 = 0.32 \pm 0.04 - (0.14 \pm 0.07)/\theta $$\end{document}The error limits are the standard deviation from the least mean‐square Arrhenius plots. The present results, combined with previously measured activation parameters for hydrogen‐atom abstraction fromc‐C6H12andn‐C6H14by CCl3radicals relative to CCl3combination, afford experimental evidence that the decay of trichloromethyl species in alkane solutions is a diffusion‐limited process. The thesis that activation energies of reactions (4) and (5) in the liquid phase are equal to their respective values in the g

ISSN:0538-8066    

DOI:10.1002/kin.550100811

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY