A quantitative scale for the extent of conjugation of substituted olefines

Zoltán Mucsi, Gregory A. Chass, Béla Viskolcz, Imre G. Csizmadia

Research output: Article

10 Citations (Scopus)


The olefinic functional group is among the most important chemical building blocks, also playing an important role in organic and bioorganic reactions. The exact description and precise quantification of the degree of the olefinic conjugation in substituted alkenes is not trivial. The present work suggests a novel, yet simple, method toward quantifying the conjugation in a general olefin group (e.g., alkenes) on a linear scale, defined as the "olefinicity scale", achieved using the computed enthalpy of hydrogenation (△H H2) of the compound examined. In the present conceptual work, the △H H2 value for allyl anion is used to define perfect conjugated character (olefinicity = +100%), while ethene represents complete absence of conjugation (olefinicity = 0%). The component △H H2 values were computed at different levels of theory, providing a near-"method- independent" measure of olefinicity. A total of 67 well-known olefinic compounds were examined to demonstrate the practicality of this protocol. For the compounds examined, a correlation has been made between the computed olefinicity percentage values and their associated proton affinities, as well as their reactivity values in a nucleophilic addition reaction; selected chemical reactions were also studied.

Original languageEnglish
Pages (from-to)7953-7962
Number of pages10
JournalJournal of Physical Chemistry A
Issue number27
Publication statusPublished - júl. 9 2009

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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