The Ethylene Dication: A Theoretical Study of the C2H42+ Potential Energy Surface

Koop Lammertsma, Mario Barzaghi, George A. Olah, John A. Pople, Alexander J. Kos, Paul V.R. Schleyer

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72 Citations (Scopus)


The C2H[formula omitted] potential energy surface was examined by ab initio molecular orbital theory corrected for electron correlation by means of Mφller-Plesset perturbation theory to third order (MP3/6-31G*) using 6-31G* (and 3-21G) optimized geometries. The perpendicular (D2d) ethylene dication, 1 (D2d), is the global and only singlet C2H[formula omitted] minimum with an estimated heat of formation of 654 kcal/mol. The rotational transition structure, 2 (D2h), is 28.1 kcal/mol higher in energy. This rotational barrier is remarkably large for such 14-electron species (compare H2BBH2 and H2B-CH2+, 10.5 and 20.1 kcal/mol, respectively). The C3v ethylidene dication, 4, 21.3 kcal/mol higher in energy than 1, is probably not a minimum, but may facilitate hydrogen scrambling. Although 1 is unstable thermodynamically toward proton loss (by 16 kcal/mol), the barriers for deprotonation (and homolytic cleavage (into two CH2+ cations)) are 68.8 and about 88.4 kcal/mol, respectively. The transition structure for cleavage of 4 into CH3+ and CH+ lies 86.5 kcal/mol above 1 in energy. These large barriers are consistent with the experimental observation of C2H[formula omitted] in the gas phase.

Original languageEnglish
Pages (from-to)5252-5257
Number of pages6
JournalJournal of the American Chemical Society
Issue number16
Publication statusPublished - Aug 1983
Externally publishedYes

ASJC Scopus subject areas

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


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