High-Accuracy Estimates for the Vinylidene-Acetylene Isomerization Energy and the Ground State Rotational Constants of: C CH2 Academic Article uri icon

abstract

  • Highly accurate calculations are reported for properties of vinylidene (H2C═C:), specifically the position of its zero-point vibrational level relative to that of acetylene and its equilibrium structure and ground state rotational constants. The isomerization energy of vinylidene calculated at the HEAT-456QP level of theory is 43.53 ± 0.15 kcal mol–1, in agreement with the previous best estimate, but associated with a much smaller uncertainty. In addition, the thermochemical calculations presented here also allow a determination of the H2CC–H bond energy of the vinyl radical at the HEAT-345(Q) level of theory, which is 77.7 ± 0.3 kcal mol–1. The equilibrium structure of vinylidene, estimated with an additivity scheme that includes treatment of correlation effects beyond CCSD(T) as well as relativistic and adiabatic (diagonal Born–Oppenheimer correction) contributions, is rCC = 1.2982 ± 0.0003 Å, rCH = 1.0844 ± 0.0003 Å, and θCCH = 120.05 ± 0.05°, with zero-point rotational constants (including vibrational contributions and electronic contributions to the moment of inertia) estimated to be A0 = 9.4925 ± 0.0150 cm–1, B0 = 1.3217 ± 0.0017 cm–1, and C0 = 1.1602 ± 0.0016 cm–1.

publication date

  • May 10, 2013