摘要:

AbstractThe reversible isomerization ofcis‐hepta‐1,3‐diene tocis‐2‐trans‐4‐heptadiene via a 1,5 hydrogen shift has been investigated kinetically at nine temperatures in the range of 475° to 531°K. Equilibrium is reached near 94% reaction. Somecis‐2‐cis‐4‐heptadiene is also formed, but at a rate some 60 times slower than thecis,transisomer. A least‐squares analysis of the data yielded the Arrhenius equation for the isomerization of thecis‐hepta‐1,3‐diene:\documentclass{article}\pagestyle{empty}\begin{document}$$ {{\log k_1 } \mathord{\left/ {\vphantom {{\log k_1 } {\sec ^{ - 1} = {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \mathord{\left/ {\vphantom {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \theta }} \right. \kern-\nulldelimiterspace} \theta }}}} \right. \kern-\nulldelimiterspace} {\sec ^{ - 1} = {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \mathord{\left/ {\vphantom {{(11.110 \pm 0.087) - ([33,210 \pm 200]{\rm cal mole}^{ - {\rm 1}} )} \theta }} \right. \kern-\nulldelimiterspace} \theta }}} $$\end{document}Possible errors in the equilibrium constant measurements are discussed, and employing an equilibrium constant calculated by using group additivity estimates together with the values ofk1, we obtained for the reverse reaction\documentclass{article}\pagestyle{empty}\begin{document}$$ {{\log k_2 } \mathord{\left/ {\vphantom {{\log k_2 } {\sec ^{ - 1} = (11.1 \pm 0.15) - ([35,800 \pm 300])}}} \right. \kern-\nulldelimiterspace} {\sec ^{ - 1} = (11.1 \pm 0.15) - ([35,800 \pm 300])}}{{{\rm cal mole}^{ - {\rm 1}} )} \mathord{\left/ {\vphantom {{{\rm cal mole}^{ - {\rm 1}} )} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}where\documentclass{article}\pagestyle{empty}\begin{document}$$ \t

ISSN:0538-8066    

DOI:10.1002/kin.550020502

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe kinetics of the acetaldehyde pyrolysis have been studied at temperatures from 450° to 525°C, at an acetaldehyde pressure of 176 torr and at 0 to 40 torr of added nitric oxide. The following products were identified and their rates of formation measured: CH4, H2, CO, CO2, C2H4, C2H6, H2O, C3H6, C2H5CHO, CH3COCH3, CH3COOCHCH2, N2, N2O, HCN, CH3NCO, and C2H5NCO. Acetaldehyde vapor was found to react with nitric oxide slowly in the dark at room temperature, the products being H2O, CH3COOCH3, CO, CO2, N2, NO2, HCN, CH3NO2, and CH3ONO2. The rates of formation of N2and C2H5NCO depend on how long the CH3CHO‐NO mixture is kept at room temperature before pyrolysis; the rates of formation of the other products depend only slightly on the mixing period.The pyrolysis of “clean” CH3CHO–NO mixtures (i.e., the results extrapolated to zero mixing time, which are independent of products formed in the cold reaction) are interpreted as follows: (1) There are two chain carriers, CH3and CH2CHO, their concentrations being interdependent and influenced by NO in different ways: the CH3radical is both generated and removed by reactions directly involving NO, whereas CH2CHO is generated only indirectly from CH3but is also removed by direct reaction with NO. (2) An important mode of initiation by NO is its addition to the carbonyl group with the formation ofwhich is converted into; this splits off OH with the formation of CH3NCO or CH3+ OCN. (3) Important modes of termination are\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm CH}_3 + {\rm NO} \to {\rm CH}_3 {\rm NO} \to {\rm CH}_2 {\rm NOH} \to {\rm HCN} + {\rm H}_2 {\rm O}} \\ {{\rm CH}_{\rm 2} {\rm CHO} + {\rm NO} \to {\rm CH}_2 ({\rm NO}){\rm CHO} \to {\rm CH}({\rm NOH}){\rm CHO} \to {\rm HCN} + {\rm H}_2 {\rm O} + {\rm CO}} \\ \end{array} $$\end{document}The steady‐state equations derived from the mechanism are shown to give a good fit to the experimental rate versus [NO] curves and, in particular, explain why there is enhancement of rate by NO at higher CH3CHO pressures and, at lower CH3CHO pressures, inhibition at low [NO] followed by enhancement at higher [NO].The cold reaction is explained in terms of chain‐propagating and chain‐branching steps resulting from the addition of several NO molecules to CH3CHO and the CH3CO radical. In the “unclean” reaction it is found that the rates of N2and C2N5NCO formation are increased by CH3NO2, CH3ONO, and CH3ONO2formed during the cold reaction. A mechanism is proposed, involving the participation of α‐nitrosoethyl nitrite, CH3CH(NO)ONO.It is suggested that there are two modes of behavior in pyrolyses in the presence of NO: (1) In the paraffins, ethers, and ketones, the effects are attributed to the addition of NO to a radical with the formation of an oxime‐like compound. (2) In the aldehydes and alkenes, where there is a hydrogen atom attached to a double‐bonded carbon atom, the behavior is explained in terms of addition of NO to the double bond followed by the format

ISSN:0538-8066    

DOI:10.1002/kin.550020503

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe gas phase reaction of iodine (2.8–43.3 torr) with methyl ethyl ketone (MEK) (7.4–303.4 torr) has been studied over the temperature range 280–355°C in a static system. The initial rate of disappearance of I2is first order in MEK and half order in I2. The rate‐determining step is the abstraction of a secondary hydrogen atom by an iodine atom:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm CH}_3 {\rm COCH}_2 {\rm CH}_2 {\rm } + {\rm I}^{\rm .} \stackrel{1}{\longrightarrow}{\rm CH}_{\rm 3} {\rm COCHCHL3 + HI} $$\end{document}wherek1is given by\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}_{{\rm 10}} ({{k_1 } \mathord{\left/ {\vphantom {{k_1 } {{\rm M}^{ - 1} \sec ^{ - 1} }}} \right. \kern-\nulldelimiterspace} {{\rm M}^{ - 1} \sec ^{ - 1} }}) = {{(10.76 \pm 0.15) - (22.0 \pm 0.4)} \mathord{\left/ {\vphantom {{(10.76 \pm 0.15) - (22.0 \pm 0.4)} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}and θ = 2.303RTin kcal/mole. This activation energy is equivalent to a secondary CH bond strength of 92.3 ± 1.4 kcal/mole and ΔH f 2980of the methylacetonyl radical = ‐16.8 ± 1.7 kcal/mole. By comparison with 95 kcal/mole for the secondary CH bond strength, when delocalization of the unpaired electron with a pi bond is not possible, the resonance stabilization of the methylacetonyl radical is calculated to be 2.7 ± 1.7 kcal/mole. This value is 10 kcal/mole less than the stabilization energy of the isoelectronic methylallyl radical. The difference in pi bond energies in the canonical forms of the methylacetonyl radical is shown to account for the variation in s

ISSN:0538-8066    

DOI:10.1002/kin.550020504

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractEquilibrium constants for the reaction CH3COCH2CH3+ I2⇌ CH3COCHICH3+ HI have been computed to fit the kinetics of the reaction of iodine atoms with methyl ethyl ketone. From a calculated value ofS 2980(CH3COCHICH3) = 93.9 ± 1.0 gibbs/mole and the experimental equilibrium constants, ΔH f0(CH3COCHICH3) is found to be −38.2 ± 0.6 kcal/mole. The Δ(ΔH f2980) value on substitution of a hydrogen atom by an iodine atom in the title compound is compared with that for isopropyl iodide. The relative instability of 2‐iodo‐3‐butanone (3.4 kcal/mole) is presented as further evidence for intramolecular coulombic interaction between partial charges in polar molecules. The unimolecular decomposition of 2‐iodo‐3‐butanone to methyl vinyl ketone and hydrogen iodide was also measured in the same system. This reaction is relatively slow compared to the formation of the above equilibrium. Rate constants for the reaction over the temperature range 281°–355°C fit the Arrhenius equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log(}{{k_{\rm 3} } \mathord{\left/ {\vphantom {{k_{\rm 3} } {{\rm sec}^{ - 1} }}} \right. \kern-\nulldelimiterspace} {{\rm sec}^{ - 1} }}{\rm )} = {\rm 13}{\rm .4} - {{(41.9 \pm 0.5)} \mathord{\left/ {\vphantom {{(41.9 \pm 0.5)} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}where θ = 2.303RTkcal/mole. The stability of both the ground and transition states is discussed in comparing this activation energy with that reported for the unimolecular elimination of hydrogen iodide from other secondary iodides. The kinetics of the reaction of hydrogen iodide with methyl vinyl ketone were also measured. The addition of HI to the double bond is not rate controlling, but it may be shown that the rate of formation of 1‐iodo‐3‐butanone is more rapid than that for 2‐iodo‐3‐butanone. Both four‐ and six‐center transition complexes and iodine atom‐catalyzed addit

ISSN:0538-8066    

DOI:10.1002/kin.550020505

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractRate constants for the bimolecular reactions of ethylene and propylene to form radicals and to form cyclobutane or its derivatives have been calculated using thermodynamic and kinetic data. Comparison of these rates with the kinetics of the thermal reactions of ethylene and propylene show that cyclobutane and its derivatives are probably not important intermediates in the processes forming radicals.

ISSN:0538-8066    

DOI:10.1002/kin.550020506

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550020507

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550020501

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY