Mechanism of the thermal decomposition and the (n-π*) excited states of azomethane

C. H. Hu, H. F. Schaefer

研究成果: Article

18 引文 斯高帕斯(Scopus)

摘要

The mechanism of azomethane decomposition CH3N=NCH3 → 2CH3· + N2 has been investigated with ab initio quantum mechanical approaches. The methods include self-consistent field (SCF), two-reference SCF (TCSCF), single- and double-excitation configuration interaction (CISD), two-reference CISD with TCSCF optimized molecular orbitals (TCSCF-CISD), single- and double-excitation coupled cluster (CCSD), and the single-, double-, and perturbative triple-excitation coupled cluster [CCSD(T)]. The `synchronous' decomposition pathway, in which a transition state of two equal distance C-N bonds is involved, was shown to be infeasible. Both cis- and trans-azomethane break one C-N bond at the first step and form the CH3 and CH3N2 radicals; then the methyldiazenyl radical further decomposes into CH3 and N2. The first C-N bond of cis- and trans-azomethane breaks without a transition state, with the predicted D0 of 46.3 kcal/mol for trans-azomethane at the TZ2P CCSD(T) level. CH3N2 decomposes through a barrier of nearly 2.3 kcal/mol into CH3 and N2, as reported by the authors previously. cis-Azomethane was predicted to be about 9.1 kcal/mol higher in energy than trans-azomethane [TZ2P CCSD(T)]. The first n → π* excited singlet (S1) and triplet (T1) states were studied also, and we report the geometries, predicted vibrational frequencies, and energetics for the vertical and adiabatic transitions of these states.

原文English
頁(從 - 到)7507-7513
頁數7
期刊Journal of physical chemistry
99
發行號19
出版狀態Published - 1995 一月 1

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physical and Theoretical Chemistry

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