Thermodynamic properties of linear carbon chain molecules with conjugated triple bonds Part 2. Free radicals C nH ( n = 2–12) and C nN ( n = 2–11)

Abstract

Reported values of rotational constants, vibrational fundamentals, excited electronic state energies, enthalpies of formation for C n ( n = 2–12) and C n N ( n = 2–11) radicals are reviewed and the recommended values selected. Molecular constants and enthalpies of formation for most of the radicals, which are known as the components of the interstellar gas or that are candidates for discovery in interstellar space, are estimated because the experimental data are not available. The similarity transference procedure is developed for the calculation of bond distances and force constants. Based on the selected values of molecular constants, the ideal gas thermodynamic functions for 21 radicals are calculated by the standard statistical mechanical method using rigid-rotor and harmonic-oscillator approximations. The calculated values of heat capacities C o p, Gibbs energies −( G o − H o 0)/ T, and enthalpies H o − H o 0, are fitted to the polynomial functions. The constants of these polynomials allow the values of C o p, − ( G o − H o 0)/ T and H o − H o 0 for considered radicals between 298.15 and 2000 K to be calculated. These constants together with the values of enthalpy of formation Δ H o (298.15 K), predicted using the estimates of bond dissociation energies are presented in this paper.