STRUCTURE AND THERMODYNAMIC FUNCTIONS OF THE ISOPROPYL RADICAL - AN ABINITIO STUDY

The equilibrium geometry, methyl group rotational barriers, and transition structure for pyramidal inversion in the isopropyl radical have been determined by use of the GAUSSIAN86 system of programs. Geometry optimization was undertaken at the unrestricted Hartree-Fock (UHF) level using the 6-31G* basis set. The structural and force field information was used to obtain vibrational frequencies and moments of inertia for overall and internal rotation. In turn, this information was used to calculate the heat capacity, entropy, enthalpy, and free energy functions by standard statistical thermodynamic methods in the rigid-rotor harmonic-oscillator approximation. With the use of the heat of formation at 298 K evaluated from kinetic data by the third-law method, values of ΔHf°, ΔGf°, and the equilibrium constant for isopropyl formation are reported as a function of temperature. © 1990 American Chemical Society.