摘要:

AbstractObservations are reported of the effect of the buffer gases He, Ne, and CF4, in the pressure range of 0–30 torr, on the branching ratio [HCl]/[DCl]of the unimolecular decompositionThe ratioR=kH/kDhas been measured in high‐pressure thermal decomposition (670–1100 K) and was shown to give a unique measure of the internal energy of the decomposing molecules and hence, with RRKM theory and pressure fall‐off data, a time scale for their decomposition.Applying the thermal data to the photolysis leads to the conclusion that excitation and decomposition are produced by the laser spike (high intensity, 70 ns FWHM) and also at a slower rate by the larger, less intense tail (1.6 μs). Added buffer gases quench the latter, leaving the former which, from measurements ofR, is shown to correspond to excitations of 115 ± 15 kcal/mol and lifetimes of ∼30 ps. No bond breaking is seen despite the high energies, in accord with theoretical expectations. The results require an enhanced rate of photon absorption by the highly excited molecules, which are about hundredfold greater than that observed for 300 K molecules. Data are also reported for C2H2F2and the secondary multiphoton photolysis of the ethylenes produced. Effects of beam geometry and wavelength a

ISSN:0538-8066    

DOI:10.1002/kin.550140402

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe prototropic rearrangement of 3‐phenyl‐1‐propenes to the corresponding 1‐phenyl‐1‐propenes was investigated in basic media utilizing 0.1Msodium ethoxide in absolute ethanol at 81°C. It was found that the effect of substituents on the rate of such isomerizations follows the order:p‐NO2>o‐Cl>m‐Cl ≥m‐F>p‐Br>o‐CH3>m‐CH3>m‐CH(CH3)2>p‐CH(CH3)2≥p‐C(CH3)3>o‐OCH3. This is consistent with first‐order kinetics and “BS E1” mechanism. Quantitative treatment in terms of Hammett's equation showed a straight line, with a slope (pvalue) of +2.25. An increase in the strength of the base was also found to

ISSN:0538-8066    

DOI:10.1002/kin.550140403

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractA study was made of the oligomerization of ethylene, initiated by the thermal decomposition of azoethane and azo‐isopropane at low temperatures, where the polymerization equilibria are shifted somewhat in the direction of the formation of products with longer carbon chains. The findings supported the picture acquired from a study of the propionaldehyde–ethylene system. Also under these conditions the oligomerization proceeds via addition between the ethylene and radicals, followed by isomerization and decomposition of the longer radicals, with a tendency to yield propylene and longer olefins. At the lower temperatures the decomposition of radicals with shorter carbon chain becomes less important in comparison with their addition reactions and, in spite of the otherwise identical mechanism, this leads to a different product distribut

ISSN:0538-8066    

DOI:10.1002/kin.550140404

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe rate constant for the reaction of ground‐state oxygen atoms with methanol has been determined between 297 and 544 K by a phase‐shift technique using mercury photosensitized decomposition of N2O to generate oxygen atoms. The relative oxygen atom concentration was monitored by the chemiluminescence from the reaction of oxygen atoms with nitric oxide. The results are accommodated by the Arrhenius expressionk1= (9.79 ± 2.71) × 1012exp[(−2267 ± 111)/T]cm3/mol·s, where the indicated uncertainties are 95% confidence limits for 10 degrees of freedom. As an incidental part of this work, the third‐body efficiency of CH3OH relative to N2O for the reaction O + NO + M → NO2+ M (M = CH3OH) was determined to be

ISSN:0538-8066    

DOI:10.1002/kin.550140405

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe kinetics of the gas‐phase elimination of several chloroesters were determined in a static system over the temperature range of 410–490°C and the pressure range of 47–236 torr. The reactions in seasoned vessels, and in the presence of a free‐radical inhibitor, are homogeneous, unimolecular, and follow a first‐order law. The temperature dependence of the rate coefficients is given by the following Arrhenius equations: for methyl 3‐chloropropionate, logk1(s−1) = (13.22 ± 0.07) ‐ (231.5 ± 1.0) kJ/mol/2.303RT; for methyl 4‐chlorobutyrate, logk1(s−1) = (13.31 ± 0.25) ‐ (221.5 ± 3.4) kJ/mol/2.303RT; and for methyl 5‐chlorovalerate, logk1(s−1) = (13.12 ± 0.25) ‐ (221.7 ± 3.2) kJ/mol/2.303RT. Rate enhancements and lactone formation reveal the participation of carbonyl oxygen of the carbomethoxy group. The order COOCH3‐5>COOCH3‐6>COOCH3‐4 in assistance is similar to the sequence of group participation in solvolysis reactions. The partial rates for the parallel eliminations to normal dehydrohalogenation products and lactones have been estimated and reported. The present results lead us to consider that an intimate ion‐pair mechanism through participation of the carbomethoxy group may we

ISSN:0538-8066    

DOI:10.1002/kin.550140406

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractRecent experimental results on the thermal decomposition of N2O5in N2are evaluated in terms of unimolecular rate theory. A theoretically consistent set of fall‐off curves is constructed which allows to identify experimental errors or misinterpretations. Limiting rate constantsk0= [N2] 2.2 × 10−3(T/300)−4.4exp(−11,080/T) cm3/molec·s over the range of 220–300 K,k∞= 9.7 × 1014(T/300)+0.1exp(−11,080/T) s−1over the range of 220–300 K, and broadening factors of the fall‐off curveFcent= exp(‐T/250) + exp(−1050/T) over the range of 220–520 K have been derived. NO2+ NO3recombination rate constants over the range of 200–300 K arekrec,0= [N2] 3.7 × 10−30(T/300)−4.1cm6/molec2·s andkrec,

ISSN:0538-8066    

DOI:10.1002/kin.550140407

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe flash photolysis resonance fluorescence technique was used to measure the rate constants of the reaction O + O2+ M → O3+ M (M = N2, O2, Ar, and He) as a function of temperature. The results for the rate constants are given byThe activation energies with N2, O2, and Ar as third bodies are equal within the experimental error, (−1370 → 340 cal/mol), and the relative third‐body efficiencies at 298 K for N2, O2, Ar, and He are 1.00, 0.99, 0.69, and 0.60, respe

ISSN:0538-8066    

DOI:10.1002/kin.550140408

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550140409

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550140410

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550140411

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY