摘要:

AbstractThe rate constant for the reaction CH3O2+ NO2→ (products) has been measured directly by flash photolysis and kinetic spectroscopy. At room temperature and at total pressures between 53 and 580 Torr,k3= (9.2 ± 0.4) × 108liter/mole sec so that the rate of formation of the probable primary product peroxymethyl nitrate (CH3O2NO2) may be significant in urban atmosphe

ISSN:0538-8066    

DOI:10.1002/kin.550120102

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractIn recent publications from this laboratory, we have shown that the fragmentation of photoexcited olefinic molecules in the vacuum UV region leads mainly to the cleavage of a C—C bond located in the ß position relative to the double bond. The allyl fragment bears away part of the excess energy of the photon. At low pressure, this excited radical is capable of undergoing further decomposition. From the pressure effect, we were able to measure the first order rate constant for this secondary fragmentation. In this paper we shall use RRKM calculations in order to get a better idea on how the energy is distributed among the primary fragments. In cases where α‐ and β;‐methallyl radicals were involved, the results show that an important part of the excess energy is located in the methallyl fragment in the 7.1 and 7.6 eV photolysis of 3‐methyl‐1‐butene, 2‐methyl‐1‐bute

ISSN:0538-8066    

DOI:10.1002/kin.550120103

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractExisting data on the self‐reactions of tertiary peroxy radicalsRO2has been reanalyzed and corrected to deduce Arrhenius parameters for both termination and nontermination paths. ForR=t‐Butyl, these are logkt(M−1sec−1) = 7.1 ‐ (7.0/θ) and logknt(M−1sec−1) = 9.4 ‐ (9.0/θ), respectively, different from those recommended by other authors. The higher magnitudes observed for termination processes of tertiary peroxy radicals like those of cumyl and 1,1‐diphenylethyl have been discussed in terms of a much greater cage recombination of cumyloxy radicals as contrasted witht‐butoxy radicals. It is shown that for benzyl peroxy radicals, theR—O ˙2bond dissociation energy is sufficiently low (18–20 kcal) that reversible dissociation intoR˙+ O2opens a competing second‐order path to fast recombinationR˙+RO ˙22→ROOR. This path is probably not important for cumyl peroxy radicals under usual experimental conditions but can become important for 1,1‐diphenyl ethyl peroxy radicals at (O2)<10−3M. At very lowRO ˙2concentrations (<10−5M), in the absence of added O2, an apparent first‐order disappearance ofRO ˙2can occur reflecting the rate determining breaking of the cumyl—O ˙2bond followed by the second step above. The thermochemistry ofRO ˙nis used to show that the reaction ofR2O4→ 2RO + O2must be concerted and cannot proceed v

ISSN:0538-8066    

DOI:10.1002/kin.550120104

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractA chain mechanism is proposed to account for the very rapid termination reactions observed between alkyl peroxy radicals containing α‐C—H bonds which are from 104to 106faster than the termination of tertiary alkyl peroxy radicals. The new mechanism iswith termination by.\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\overline {{\rm CHOO}} $\end{document}is the zwitterion originally postulated by Criegee to account for the chemistry of O3‐olefin addition. Heats of formation are estimated for\documentclass{article}\pagestyle{empty}\begin{document}$ \overline {{\rm CH}_2 {\rm OO,}} {\rm }\overline {{\rm RCHOO}} $\end{document}, and\documentclass{article}\pagestyle{empty}\begin{document}$ ({\rm C}\overline {{\rm H}_3 )_2 {\rm COO}} $\end{document}and it is shown that all steps in the mechanism are exothermic. The second step can account for (1Δ)O2which has been observed.k1is estimated to be 109–2/θliter/Msec where θ = 2.303RTin kcal/mole. The second and third steps constitute a chain termination process where chain length is estimated at from 2 to 10. This mechanism for the first time accounts for minor products such as acid andROOH found in termination reactions. Trioxide (step 3) is shown to be important below 30°C or in very short time observations (<10 s at 30°C). Solvent effects are also shown to be compatible with the

ISSN:0538-8066    

DOI:10.1002/kin.550120105

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetics of the slow oxidation of CO in the presence of H2have been studied above the second explosion limit for the mixture 2CO + O2+X% H2at the temperature range of 530–570°C, pressures from 300 to 530 torr, and hydrogen contents of 1.1, 2.8, and 5.7%. The second explosion limit has been experimentally determined for the mixture of 2CO + O2containing 1.0, 3.0, and 5.7% H2. On the basis of the oxidation scheme of CO in the presence of H2, which includes the accepted mechanism of oxidation of hydrogen supplemented by the reactions in which CO takes part, the second explosion limit and the profiles of the slow reaction are calculated by computer methods. The agreement found between experimental and calculated values allows one to conclude that the scheme under consideration rather completely described the slow reaction above the second limit and the occurrence of the second explosion limit in the mixture CO–O2–H2. The rate constant for the reaction HO2+ CO → OH + CO2was calculated from the experimental data and was found to agree with previous determ

ISSN:0538-8066    

DOI:10.1002/kin.550120106

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550120101

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY