摘要:

AbstractAn analysis of the atmospheric observations of O2(1δg) in the dayglow and twilight confirms the crude experimental assessments of Brown [1] and the conclusions that can be made from recent work of Westenberg, Roscoe, and DeHaas [2]that the reaction\documentclass{article}\pagestyle{empty}\begin{document}$${\rm H} + {\rm O}_{\rm 2} (^1 \Delta g) \to {\rm OH} + {\rm O}$$\end{document}is relatively slow, much slower than was expected or can be explained easily in theoretical terms. Using a value for the concentration of atomic hydrogen at 85 km, an upper limit rate of 3×10−13cm3molecule−1sec−1would be compatible with current atmospheric models. An evaluation of the available data for the rates of several reactions involving ground state or electronically excited species, for which the values are reasonably well established, is included to better analyze the general effects of an electronically excited reactant. This further illustrates the unusual slowness of the H + O2(1Δg)

ISSN:0538-8066    

DOI:10.1002/kin.550040302

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe pyrolysis of ethyl acetate has been studied by the very low‐pressure pyrolysis (VLPP) technique. The results obtained agree well with the previously determined high‐pressure Arrhenius parameters where logk∞= 12.6 − 48.0/θ. The rate constants given by these parameters have also been shown to be consistent with the predictions of the RRK and RRKM theories and demonstrate the applicability of the technique to the study of thermal decomp

ISSN:0538-8066    

DOI:10.1002/kin.550040303

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractValues of the rate constants for allyl‐radical abstraction from toluene and allyl‐radical recombination have been recalculated in the light of recent data on butene‐1 decomposition. The rate of recombination is in good agreement with that found by Van den Bergh and Callear [13] and the cross‐combination ratio for the allyl + methyl system has a “normal” value of almost 4. It is concluded that allyl radicals behave like alkyl radicals in respect of their rates of reaction with oth

ISSN:0538-8066    

DOI:10.1002/kin.550040304

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractPrevious studies by Buckler and Norrish of the second limit of CO and O2mixtures containing small amounts (0.25–10%) of H2have been used to obtain the velocity constant of the reaction\documentclass{article}\pagestyle{empty}\begin{document}$${\rm O} + {\rm CO} + {\rm M = CO}_{\rm 2} + {\rm M}$$\end{document}These estimates ofk33= 3.9 × 108and 3.5 × 108liter2mole−2sec−1(M  H2) at 500° and 560°C, respectively, have been combined with other estimates over the range 300°–3500°K to givek33= 3.0 × 108exp (−3000/RT) for M  Ar; the considerable scatter in the available points does not encourage any great confidence in this expression and may be attributed at least partly to the different molecules used as M by different workers. For KCl‐coated and CsCl‐coated vessels at 540°C, studies of the second limit of H2+ O2mixtures, to which CO has been added, have indicated that with both the surfaces, the effect of CO on the limit is masked by changes in the surface nature. In the case of CsCl, the results have enabled a lower limit of about 0.6 to be obtained for the efficiency of CO relative to H2in the reaction\documentclass{article}\pagestyle{empty}\begin{document}$${\rm H} + {\rm O}_{\rm 2} + {\rm M = HO}_{\rm 2} + {\rm M}$$\end{document}Use of a computer treatment to interpret the second limit of CO + H2+ O2mixtures in aged boric‐acid‐coated vessels at 500°C gives a value ofmCO= 0.74 ± 0.04 together with an estimate ofk32(H + CO + M″ = HCO + M″)/k4= 0.022 ± 0.003, which leads tok32= 2.3 ×

ISSN:0538-8066    

DOI:10.1002/kin.550040305

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe vibrational excitation of HF and DF and the energy transfer efficiencies for various collision partners were investigated over the temperature and pressure ranges of 1400°K to 4100°K and 0.1 to 0.3 atm, respectively. The extent of excitation was determined as a function of time by continuously monitoring the infrared emission intensity at the center of the 1–0 vibration‐rotation band of the molecule. Collisional efficiencies of HF, N2, O2, F, Cl, and DF in relaxing HF and of DF, HF, and N2in relaxing DF are reported. A comparison with relaxation data for pure HF taken at lower temperature suggests that long‐range attractive forces are mechanistically of major importance in the relaxation process. The relatively high efficiency of atomic chlorine in relaxing HF, i.e., (τP)HF–HF/(τP)HF–C1≥ 5 at 3000°K is discussed in terms of our previous result for atomic fluorine, i.e., (τP)H

ISSN:0538-8066    

DOI:10.1002/kin.550040306

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractEffects of deuterium substitution in propylene on the relative rates of H(D) atom abstraction from and addition to the olefin, and on the orientation of H(D) atom addition, have been studied in the gas phase at room temperature. Effects of isotopic substitution of the olefinic hydrogen atoms on abstraction could not be observed, but abstraction is reduced five‐ to tenfold by deuteration of the methyl group. Deuteration of either olefinic position enhances the rate of addition to the substituted carbon atom. Disproportionation‐combination ratios for deuterium‐substituted propyl radicals are not greatly different from those for unsubstituted radicals, the largest effect being for C3D7radicals, for which the overallkd/kcis reduced 1

ISSN:0538-8066    

DOI:10.1002/kin.550040307

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe position of abstraction by H atoms from ethylene, propylene, butene‐1, andcis‐ andtrans‐butene‐2 and the rates of abstraction relative to addition have been measured at 25°C. Only allylic abstraction was observed. From ethylene, abstraction relative to addition was ≤3×10−4. For propylene, butene‐1,cis‐butene‐2, andtrans‐butene‐2, abstraction occurred on 0.2%, 1.6%, 1.5%, and 0.9% of the reactive encounters, if dis‐proprotionation‐combination ratios for allyl and alkyl radicals are similar to

ISSN:0538-8066    

DOI:10.1002/kin.550040308

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractSecondary kinetic isotope effects occur in radical additions to deuterated olefins. Substitution of a deuterium at a carbon undergoing ansp2tosp3hybridization‐change during reaction, Cβin eq. (1), leads to aninverse isotope effect of 3–5% (kH/kD= 0.95–0.97). The effect at a carbon going from an olefinic to a radical center, Cαin eq. (1), generally has been assumed to be negligible, since a nominalsp2hybridization is maintained throughout reaction. Using new, sensitive instrumentation for radioactivity determination and a recently developed quench correction technique, we now find that there is a small, normal isotope effect (kH/kT1) associated with a change from olefin to radical. Specifically, when R· is the polystyryl radical, X is phenyl, and the α‐C bears a tritium,kH/kT= 1.04. This result is discussed in relation to recent data on cycloadditio

ISSN:0538-8066    

DOI:10.1002/kin.550040309

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractIn polychloro‐2,2‐difluoropropanes, where a large inductive effect results in relatively low reactivity to chlorination, the presence of additional chlorine causes an increased reactivity of the hydrogens geminal to the chlorine and a reduced reactivity of the remote (third carbon) hydrogens. The ways in which resonance, inductive effect, and steric crowding interact in the rates of chlorination of polar molecules are discus

ISSN:0538-8066    

DOI:10.1002/kin.550040310

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractMeasurements of theD(RNO) bond strength in some C‐nitrosocompounds have been made using an electron impact method. The appearance potential of the radical ion (R+) has been determined, theD(RNO) bond energy being obtained from the relation\documentclass{article}\pagestyle{empty}\begin{document}$$D{\rm (R} - {\rm NO) = }AP{\rm (R}^{\rm + } {\rm)} - IP({\rm R}.)$$\end{document}The values obtained are:D(C6H5NO) = 41 kcal/mole,D(t‐C4H9NO) = 34 kcal/mole,D(t‐C5H11NO) = 36 kcal/mole andD(i‐C3H7NO) = 36.5 kcal/mole. These values are in good agreement with the numerous estimations of Benson and coworkers and confirm that the CN bond strength in C‐nitrosocompounds is very much less than in nitr

ISSN:0538-8066    

DOI:10.1002/kin.550040311

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY