摘要:

AbstractThe gas phase reaction I2+ HCOOCH3→ HI + CH3I + CO2has been studied spectrophotometrically in a static system over the pressure ranges I2(6–39 torr) and HCOOMe (28–360 torr). In the temperature range 293–356°, the initial rate of disappearance of I2is first order in [HCOOMe] and half‐order in [I2]. The rate determining step iswherek1is given by\documentclass{article}\pagestyle{empty}\begin{document}$$\log _{10} \left({k_1 /{\rm M}^{- 1} \sec ^{- 1}} \right) = \left({9.6 \pm 0.3} \right) - \left({22.4 \pm 0.8} \right)/\theta $$\end{document}where θ = 2.303RTin kcal/mole. This activation energy gives a carbonyl CH bond strength of 92.7 kcal/mole. At 356° there was no evidence of abstraction of a methoxy hydrogen, so a lower limit of 100 kcal/mole may be placed on this CH bond strength. These ester CH bond strengths are discussed in relation to comparable values in al

ISSN:0538-8066    

DOI:10.1002/kin.550010502

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe relative rates of addition of difluorocarbene to a series of methyl‐substituted olefins have been determined and correlated with similar data for dichlorocarbene, chlorofluorocarbene and ground‐state oxygen atoms. The electrophilic nature and stabilization of difluorocarbene by the fluorine substituents is discussed. Relative activation energies for the difluorocyclopropane‐forming reaction have been estimated and correlated with properties of the olefins as derived from molecular orbital t

ISSN:0538-8066    

DOI:10.1002/kin.550010503

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractData on the kinetics of S2F10pyrolysis, which gives SF4+ SF6, have been reinterpreted to give a value for the equilibrium constant of S2F10⇆ SF4+ SF6. This, together with statistical estimates of the entropy and heat capacity of S2F10, can be used to give for this reaction values of ΔH 298°= 19.7 ± 1.0 kcal/mole and ΔS 300°= 47.6 ± 2 gibbs/mole. ΔH f°(S2F10) = –494 kcal/mole. A compatible mechanism is shown to be S2F10⇆ 2SF5(fast); 2SF5⇆ SF6+ SF4(slow) with step 2 rate‐determining. The overall, best first order rate constant is proposed askmeas= 1017.42–43.0/θsec−1=K1k2, where θ = 2.303RTin kcal/mole.Independent measurements of δH f°andS° for the SF5radical, permits the evaluation of the equilibrium constantK1= 108.92–(27.1 ± 6)/θl./mole‐sec and yieldsk2= 108.50–15.9/θl./mole‐sec. The observed homogeneous catalysis by NO and CHCl  CHCl can be explained in terms of a direct abstraction of F from S2F10: C + S2F10→ CF + S2F9, followed by S2F9

ISSN:0538-8066    

DOI:10.1002/kin.550010504

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe intramolecular elimination of isobutene from 2‐d1‐triisobutylaluminum has been studied in the gas phase for temperatures ranging between 102.4 and 184.6°C. The reaction is apparently homogeneous and obeys the first order rate law, yielding the following Arrhenius relationship:\documentclass{article}\pagestyle{empty}\begin{document}$$ \log \,k_{{\rm el}im} \left( {\sec ^{ - 1} } \right) = 11.1 - {{27.2} \mathord{\left/ {\vphantom {{27.2} {\theta \,{\rm where}\,\theta \,{\rm equals}\,4.58 \times 10^{ - 3} }}} \right. \kern-\nulldelimiterspace} {\theta \,{\rm where}\,\theta \,{\rm equals}\,4.58 \times 10^{ - 3} }}T\left( {{}^ \circ {\rm K}} \right)\,{\rm in}\,{\rm units}\,{\rm of}\,{{{\rm kcal}} \mathord{\left/ {\vphantom {{{\rm kcal}} {{\rm mole}{\rm .}}}} \right. \kern-\nulldelimiterspace} {{\rm mole}{\rm .}}} $$\end{document}Excess ethylene was added to the starting material in order to avoid complications from the backreaction. The cyclic 4‐center nature of the transition state proposed earlier has been unequivocally demonstrated by deuterium labelling. Mass‐spectral analyses show that the isobutene formed contains no deuterium. The hydrolyses products of the mixed trialkylaluminum formed during the reaction consist of monodeuteroethane and 2‐d1‐isobutane. The observed negative entropy of activation of ∼12 cal/°‐mole agrees with prediction and implies a reasonably tight transition state structure. Combined with the corresponding data for the non deuterized Al(i‐bu)3reported earlier, these data result in a primary kinetic deuterium isotope effect ofkH/kD= 1.3 × 100.6/θcorresponding to a ratio of the isotopic rate constants of 3.7 at 25°C. This result is in excellent agreement with a predicted value of 1.4 × 100.7/θand it is in line with literature data on similar reactions involving cyclic tr

ISSN:0538-8066    

DOI:10.1002/kin.550010505

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe gas phase isomerization of 1,1‐dimethyl‐2‐vinylcyclopropane tocis‐2‐methylhexa‐1,4‐diene has been studied in a static system. The isomerization is homogeneous and kinetically first order. The rate constants were independent of initial reactant pressure in the range 0.6 to 2 torr and of added nitrogen up to 180 torr. Rate constants determined at 10 temperatures in the range 200 to 254°C fitted the Arrhenius equationk= 1011.41±0.02exp (−33,540 ± 47 cal/RT) sec−1The lowAfactor and activation energy are consistent with a concerted 1,5‐hydrogen migration via a “tight”

ISSN:0538-8066    

DOI:10.1002/kin.550010506

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010507

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010508

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010509

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010510

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010511

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY