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Where is the Limit to which the Qualitative Theory of Chemical Reactivity can be Extended? Study of Dienophilic Activity of Cyanoethylenes

Michael V. Basilevsky ; Karpov Institute of Physical Chemistry, ul. Obukha 10, Moscow 107120, USSR
Noham N. Weinberg ; Karpov Institute of Physical Chemistry, ul. Obukha 10, Moscow 107120, USSR
Victor M. Zhulin ; Karpov Institute of Physical Chemistry, ul. Obukha 10, Moscow 107120, USSR


Puni tekst: engleski pdf 10.153 Kb

str. 1423-1444

preuzimanja: 125

citiraj


Sažetak

A qualitative quantum-chemical approach, based on the stabilization
energy method, is applied to discuss the mechanism and
some kinetic regularities observed in Diels-Alder (DA) reactions
of cyanoethylenes with cyclopentadiene and phencyclone. For the
former reaction series the polar effect predominates over the localizationeffect and both the regular activity sequence and the great
range of the rate constants can be understood as a result of the
charge transfer from diene to dienophile in a synchronous transition
state (TS). The inversion of the regulaT activity sequence
observed for the latter reaction series seems to be caused by localizationeffects in asynchronous TS. The relative weakening of the
charge transfer is associated with the increased role of electron
correlation. Possible distortions of the TS structure within a
reaction series are analyzed. The shift of the TS a account when considering the kinetic data. The. TS shift along
the symmetric coordinate is negligible. The influence of the prereaction
complex formation on DA reaction kinetics is found to be
inconsequential for the reactions under consideration.

Ključne riječi

Hrčak ID:

194034

URI

https://hrcak.srce.hr/194034

Posjeta: 261 *