Isomerization reactions on the lowest potential energy hypersurface of triplet vinylidene and triplet acetylene

Journal Article · Mon Mar 15 04:00:00 EST 1993 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.464980· OSTI ID:6855116

Vacek, G; Thomas, J R; DeLeeuw, B J; Yamaguchi, Y; Schaefer, III, H F ^[1]

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1. Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States)

Triplet vinylidene, first predicted to have a sizeable barrier to unimolecular rearrangement in 1978 by theory, has now been observed under three different sets of experimental conditions. In order to quantitatively characterize the potential energy hypersurface of triplet vinylidene and triplet acetylene, high-level [ital ab] [ital initio] quantum mechanical methods have been employed. Basis sets as large as triple zeta plus two sets of polarization functions augmented with higher angular momentum functions [TZ(2[ital df],2[ital pd])] have been utilized in conjunction with correlated methods as sophisticated as the coupled cluster approach including all single, double, and perturbative triple excitations [CCSD(T)]. Of particular interest are predictions of the zero-point vibrational energy corrected barriers for rearrangement of [ital [tilde a]] [sup 3][ital B][sub 2] vinylidene to [ital [tilde b]] [sup 3][ital B][sub [ital u]] [ital trans]-bent acetylene and of [ital cis]-bent [ital [tilde a]] [sup 3][ital B][sub 2] acetylene to [ital trans]-bent [ital [tilde b]] [sup 3][ital B][sub [ital u]] acetylene. At the highest level of theory used here, TZ(2[ital df],2[ital pd]) CCSD(T), these are predicted to be 47.9 and 13.0 kcal/mol, respectively. The physical properties of [ital [tilde a]] [sup 3][ital B][sub 2] vinylidene, including the dipole moment, harmonic vibrational frequencies, and the infrared intensities, have also been reported.

• DOE Contract Number: FG09-87ER13811
• OSTI ID: 6855116
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 98:6; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACETYLENE
ALKYNES
CHEMICAL REACTIONS
ENERGY
HYDROCARBONS
ISOMERIZATION
MECHANICS
MULTIPLETS
ORGANIC COMPOUNDS
POTENTIAL ENERGY
QUANTUM MECHANICS
RADICALS
TRIPLETS
VINYLIDENE RADICALS