A Comparison of the Energies of Double Bonds of Second-Row Elements with Carbon and Silicon

Paul von Rague Schleyer, Daniel Kost

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214 Scopus citations


Theoretical π-bond energies (Eπ) are evaluated for the double bond systems H2Y=XHn (Y = C, Si; X = B, C, N, O, Al, Si, P, S) employing the MP4SDTQ/6-31G*//6-31G* + ZPE level of theory. The difference in energy between two single bonds, X-Y, and a double bond, X= Y, is calculated by means of isodesmic equations. Eπ is given by subtraction of this difference from the dissociation energies of the single bond system, D0°. Si=X bonds are found to have significantly lower Eπ energies than the corresponding C—X bonds; for each series, C~X and Si=X, the π-bond energies for both first-and second-row substituents correlate with the electronegativities of X. When electronegativity differences between carbon and silicon and among the X groups is taken into account, second- and first-row π-bond energies are similar. Families of linear correlations are also observed for Eπ and Y=X bond lengths. Alternative procedures for estimating π bond energies (rotation barriers and diradical components) are criticized.

Original languageEnglish
Pages (from-to)2105-2109
Number of pages5
JournalJournal of the American Chemical Society
Issue number7
StatePublished - 1 Jan 1988

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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