ChemInform Abstract: Substitution Effects on the Properties of Unsaturated Carbenes: Fluorovinylidene (HFC=C:)

DeLeeuw, Bradley J.; Fermann, Justin T.; Xie, Y.; Schaefer, Henry F.

doi:10.1002/chin.199324099

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“…By contrast, in the 3 A″ state of the iso-form the spin−orbit interactions have been calculated very small even for bromine systems (<0.1 cm −1 for C 2 HBr), but the equilibrium energy of this 3 A″ state is still lying below its dissociation limit and the state can thus be considered as potentially stable. The comparison with previous calculated values of these triplet states for C 2 HF 40,42 shows good agreement and can validate our results for the other halogen systems. In these triplet states, the CC and the CX bond lengths are found larger than in the linear X 1 Σ + ground state.…”

Section: Energetic Diagramssupporting

confidence: 90%

Energetic Diagrams and Structural Properties of Monohaloacetylenes HC≡CX (X = F, Cl, Br)

2016

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Highly correlated electronic wave functions within the Multi Reference Configuration Interaction (MRCI) approach are used to study the stability and the formation processes of the monohaloacetylenes HCCX and monohalovinylidenes C2HX (X = F, Cl, Br) in their electronic ground state. These tetra-atomics can be formed through the reaction of triatomic fragments C2F, C2Cl, and C2Br with a hydrogen atom or of C2H with halogen atoms via barrierless reactions, whereas the reactions between the diatomics [C2 + HX] need to overcome barriers of 1.70, 0.89, and 0.58 eV for X = F, Cl, and Br. It is found that the linear HCCX isomers, in singlet symmetry, are more stable than the singlet C2HX iso-forms by 1.995, 2.083, and 1.958 eV for X = F, Cl, and Br. The very small isomerization barriers from iso to linear forms are calculated 0.067, 0.044, and 0.100 eV for F, Cl, and Br systems. The dissociation energies of the HCCX systems (without ZPE corrections), resulting from the breaking of the CX bond, are calculated to be 5.647, 4.691, and 4.129 eV for X = F, Cl, Br, respectively. At the equilibrium geometry of the X(1)Σ(+) state of HCCX, the vertical excitation energies in singlet and triplet symmetries are all larger than the respective dissociation energies. Stable excited states are found only as (3)A', (3)A″, and (1)A″ monohalovinylidene structures.

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Section: Energetic Diagramssupporting

confidence: 90%