Conservation of bond order during hydrogenolysis and dehydrogenation reactions

Paul Blowers, Rich Masel

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Previous investigations have used bond-order conservation to make useful predictions about surface phenomena, but the accuracy of bond-order conservation for complicated processes is unknown. In this paper, we use ab-initio calculations at the MP2 = (full)/6-31g* level to investigate bond-order conservation, and its implications, for the following gas-phase reactions: H* + CH3OH →CH3H*+ OH, H* + CH3OH→HOH* + CH3, H*+ CH3OH →HH*+ CH2OH, H*+ CH3OH →HH*+ CH3O, H* + CH3OH→H + CH2H*OH, H* + CH3OH→H + CH3OH*. We find that bond order is approximately conserved during the atom transfer reactions, but is not conserved during hydrogenolysis reactions. The transition state is predicted to be too early for hydrogen exchange on oxygen, too late for the hydrogenolysis reactions, and about right for the hydrogen transfer reactions. Even though the transition-state structures are not well represented using conserved total bond order, the energies of the barriers predicted this way are off by only 1-2 kcal mol-1. Physically, the potential energy surfaces are so flat near the transition state that errors in geometry do not produce significant errors in energy. Consequently, although bond-order conservation does not predict the correct transition states geometry the energies of the transition state predicted with bond-order conserved pathways are very close to their ab initio values.

Original languageEnglish (US)
Pages (from-to)238-246
Number of pages9
JournalSurface Science
Volume417
Issue number2-3
DOIs
StatePublished - Nov 20 1998
Externally publishedYes

Keywords

  • Ab initio quantum chemical methods and calculations
  • Alcohols
  • Hydrogen
  • Models of surface chemical reactions
  • Semi-empirical models and model calculations

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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