Regioselectivity in cycloaddition reaction between phosphaacetylene and diazomethane: An ab initio study

L. Nyulászi, Péter Várnai, Wolfgang Eisfeld, Manfred Regitz

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Abstract

The [3 + 2] cycloaddition reaction of phosphaacetylene with diazomethane was investigated by means of high level ab initio calculations. It was deduced that the aromatic diazaphosphole is formed via a nonaromatic intermediate. The regiospecificity of the reaction is thus determined by the energy difference between the two transition states that lead to the two possible regioisomeric intermediates. Of the transition states in the concerted pathways, the one leading to the regioisomer with two PC bonds (3) was found to be more stable at all the levels of theory investigated, including coupled-cluster singles doubles (CCSD)(T)/6-311 + G*//Møller-Plessett(MP)2/6-311 + G* (+basis set superposition, BSSE, correction). The energy difference between the two transition states, however, is always less than 2 kcal/mol. When the free energies in the two reactions are calculated by use of the harmonic frequencies, the energy separation between the two transition structures remains practically unchanged. The free energy of activation ΔG was 21 kcal/mol at the CCSD(T)/6-311 + G* level of theory and use of the MP2/6-31 + G* frequencies. At the MP2 level, a rather stable complex is obtained in the initial phase of the reaction. However, the stability of the complexes decreases at the CCSD(T) level, and application of the BSSE correction results in unstable complexes.

Original languageEnglish
Pages (from-to)609-616
Number of pages8
JournalJournal of Computational Chemistry
Volume18
Issue number5
Publication statusPublished - Apr 15 1997

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Diazomethane
Regioselectivity
Cycloaddition
Transition State
Free energy
Free Energy
Energy
Chemical activation
Ab Initio Calculations
Superposition
Activation
Pathway
Harmonic
Unstable
Decrease

ASJC Scopus subject areas

  • Chemistry(all)
  • Safety, Risk, Reliability and Quality

Cite this

Regioselectivity in cycloaddition reaction between phosphaacetylene and diazomethane : An ab initio study. / Nyulászi, L.; Várnai, Péter; Eisfeld, Wolfgang; Regitz, Manfred.

In: Journal of Computational Chemistry, Vol. 18, No. 5, 15.04.1997, p. 609-616.

Research output: Contribution to journalArticle

Nyulászi, L. ; Várnai, Péter ; Eisfeld, Wolfgang ; Regitz, Manfred. / Regioselectivity in cycloaddition reaction between phosphaacetylene and diazomethane : An ab initio study. In: Journal of Computational Chemistry. 1997 ; Vol. 18, No. 5. pp. 609-616.
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