摘要:

AbstractTrimethylene sulfone and 3methyl sulfolane have been pyrolyzed using a modification of the toluene flow method and a comparative rate technique. The main decomposition reactions arewherek1=1016.1±0.3exp(−28,100±500/T) sec−1andk2=1016.1±0.4exp(−33,200±7

ISSN:0538-8066    

DOI:10.1002/kin.550070602

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractRate constants and activation parameters are reported for the decarboxylation ofn‐butylmalonic acid in four normal alkanols (hexanol1, octanol1, decanol1, and dodecanol1) and in five amines (aniline,N‐methylaniline,N‐ethylaniline,N‐n‐propylaniline, andN‐n‐butylaniline). Both ΔH‡ and ΔS‡ of the reaction in both homologous series decrease regularly with increasing length of the hydrocarbon chain of solvent. If we compare data for the reaction in alkanol–amine pairs containing the same total number of carbon atoms in the molecule, we find that the ΔH‡ values are identical, but that the value of ΔS‡ is 0.8 eu/mole higher for the reaction in the amines as compared with the alcohol. The rate constant, at all temperatures, is 1.5 times as large in the amine as it is in the corresponding alcohol. Empirical equations are deduced relating the parameters ΔH‡ ΔS‡ ΔG‡ andkof the reaction to the parametersnandT, wherenis the total number of carbon atoms in the solvent molecule andTis the absolute temperature. The results reported herein are compared wi

ISSN:0538-8066    

DOI:10.1002/kin.550070603

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe homogeneous exchange reaction between tetradeutero methane and ammonia was studied behind reflected shocks in a single‐pulse shock tube over the temperature range of 1300–1800°K. The rate of production of CD3H at the early stages of the reaction in mixtures ranging between 1‐4.5% NH3and 1–4.3% CD4in argon is given byd[CD3H]/dt=kb[CD4]0[NH3]0, wherekb=8 × 1016exp (−65.3 × 103/RT) cm3/mole·sec. This activation energy is considerably lower than the one that may be expected on the basis of a pure free radical mechanism. It is rationalized by C2D6impurities in the methane. No clear answer can be obtained regarding the role of a four‐center intermediate i

ISSN:0538-8066    

DOI:10.1002/kin.550070604

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractExact solution methods are developed for the complex kinetic and product distribution equations encountered in a particular type of competitive recombination or crossover reaction involving “cages.” Pertinent reaction systems are those where scavenging of the intermediates escaping the cages is restricted to species similar to these intermediates, thereby limiting potentially undesired side effects of the scavenger. The trustworthiness of the reaction constants which may be obtained, particularly the fraction of recombination occurring within the cage, are analyzed in terms of sources of possible error. Several extensions of the method are briefly discussed, such as in distinctions between inter‐ and intramolecular rearrangements. Full detailing of the solution methods should facilitate their use in the analysis of similar reaction sc

ISSN:0538-8066    

DOI:10.1002/kin.550070605

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe very low‐pressure pyrolysis (VLPP) technique has been used to study the pyrolysis ofn‐propyl cyanide over the temperature range of 1090–1250°K. Decomposition proceeds via two pathways, C2C3bond fission and C3C4bond fission, with the former accounting for>90% of the overall decomposition. Application of unimolecular reaction rate theory shows that the experimental unimolecular rate constants for C2C3fission are consistent with the high‐pressure Arrhenius parameters given by\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_1 (\sec ^{ - 1}) = (15.4 \pm 0.3) - (76.7 \pm 1.7)/\theta $$\end{document}where θ=2.303RTkcal/mole. The activation energy leads toDH2980[C2H5CH2CN]=76.9±1.7 kcal/mole and ΔH ƒ,2980(ĊH2CN, g)=58.5±2.2 kcal/mole. The stabilization energy of the cyanomethyl radical has been found to be 5.1±2.6 kcal/mole, which is the same as the value for the α‐cyanoethyl radical. This result suggests thatDH 2980[CH2(CN)H] ∼ 93 kcal/mole, which is considerably higher than previously reported. The value obtained for ΔHƒ0(ĊH2CN) should be usable for prediction of the activation energy for C2C3fission in primary alkyl cyanides, and this has been confirmed by a study of the VLPP of isobutyl cyanide over the temperature range of 1011–1123°K. The decomposition reactions parallel those forn‐propyl cyanide, and the experimental data for C2C3fission are compatible with the Arrhenius expression\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_5 (\sec ^{ - 1}) = (15.4 \pm 0.3) - (73.1 \pm 1.7)/\theta $$\end{document}A significant finding of this work is that HCN elimination from either compound is practically nonexistent under the experimental conditions. Decomposition of the radical, CH3CHCH2CN, generated by C3C4fission in isobutyl cyanide, yields vinyl cyanide and not the expected product, crotonitrile. This may be explained by a radical isomerization

ISSN:0538-8066    

DOI:10.1002/kin.550070606

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA new method was developed for the calculation of the resonance substituent constants of the two‐parameter Taft equation logksub/k0=ρ*σ*+r*σr. It is based on a relationship between the spin density in free radicals and the rate constants of radical substitution reactions of CH3. Possibilities and limitations of the application of this correlation equation to the investigation of substitution and addition radical reactions are discu

ISSN:0538-8066    

DOI:10.1002/kin.550070607

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe specific decomposition rates of chemically activated methylcyclobutane produced from CH2(1A1) reaction with cyclobutane have been determined. CH2(1A1)was produced from ketene photolyses at 3340 and 3130 Å and from diazomethane photolyses at 4358 and 3660 Å. Comparisons of the excitation energies of the methylcyclobutane, determined by RRKM theory calculations, and the experimental results for the ketene systems, with thermochemically predicted maximum excitation energies, favor an ArrheniusAfactor in the range of 5 × 1015to 1 × 1016sec−1for methylcyclobutane. This result is consistent with (1) the comparison of RRKM theory calculations and the experimental unimolecular falloff for methylcyclobutane, (2) the comparison of experimentalAfactors for cyclobutane and other alkylcyclobutane decompositions, and (3) two out of three reported experimentalAfactors for methylcyclobutane. An analysis of these and previous results leads to a value of the CH2(1A1) ↔ CH2(3B1) energy splitting of 9±3 k

ISSN:0538-8066    

DOI:10.1002/kin.550070608

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractPrevious experimentation on the initial stages of the oxygen‐ethane reaction at temperatures near 600°C demonstrated the existence of a significant induction period under homogeneous conditions. Below 0.13% conversion, the rate with oxygen is less than the rate of ethane pyrolysis in the absence of oxygen. Experiments were conducted with mixtures of ∼1% ethane and ∼0.4% oxygen in nitrogen using the “wall‐less” technique. Mathematical simulations of the oxidative and simple pyrolyses of ethane were established by a numerical analysis. The experimentally observed induction period and the mechanisms previously proposed are supported by these computations. Steady‐state conditions are much more slowly attained in the presence of oxygen than

ISSN:0538-8066    

DOI:10.1002/kin.550070609

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe mechanism and kinetics of the reaction of O(3P) atoms with propane were investigated using molecular modulation spectroscopy, with the O(3P) atoms being generated by the Hg photosensitized decomposition of N2O. The absorption spectrum of theX2II3/2state of OH was observed in the ultraviolet between 307 and 309 nm, and it was confirmed that OH was the product of the O(3P) reaction with propane. The rate constants for the reactions of O(3P) and OH with propane were determined to be 3.9±0.7±1010and 1.19±0.05±1012cm3/mole·sec, respectively, atT=56

ISSN:0538-8066    

DOI:10.1002/kin.550070610

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractKinetics of protonation of Li+, Na+, K+, and Cs+salts of anthracene radical anions (A−·,Cat+) and dianions (A2−, 2Cat+) by MeOH and MeOD in tetrahydrofuran (THF) and dimethoxyethane (DME) led to the determination of the isotope effect (kH/kD) in the following reactions:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm MeOH(MeOD) + A}\bar \cdot {\rm,Cat}^{\rm + } \to MeO^ - {\rm,Cat}^{\rm + } {\rm + AH} \cdot {\rm (D)} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm (MeOH)}_{\rm 2} {\rm or (MeOD)}_{\rm 2} {\rm + A}\bar \cdot {\rm,Cat}^{\rm + } \to {\rm MeOH,MeO}^ - {\rm,Cat}^{\rm + } {\rm + AH} \cdot {\rm (D)} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm MeOH (MeOD) + A}^{{\rm 2 - }} {\rm,2Cat}^{\rm + } \to {\rm MeO}^ - {\rm,Cat}^{\rm + } {\rm + AH(D)}^{{\rm - 1}},{\rm Cat}^{\rm +} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm MeOH (MeOD) + (A,Cat}^{\rm + } {\rm,A}^{{\rm 2 - }} {\rm,Cat}^{\rm + }) \to {\rm MeO}^ - {\rm,Cat}^{\rm + } {\rm + A + AH(D)}^{\rm - },{\rm Cat}^{\rm +} $$\end{document}Studies of cation and solvent influence on the rate constants of these reactions and on the magnitude of the isotope effect permitted us to draw some conclusions about the structure of the pertinent transition states. It seems that only the tight A−·,Na+pairs participate in the protonation, and on this basis the fraction of tight ion paris of A−·,Na+in DME was estimated. Our results have been compared with data reported in the

ISSN:0538-8066    

DOI:10.1002/kin.550070611

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY