Thermodynamic Properties (ΔHf(298), S(298), and Cp(T) (300 ≤ T ≤ 1500)) of Fluorinated Propanes

Abstract

Thermodynamic properties (ΔHf°298, S°298, and Cp(T) (300 ≤ T/K ≤ 1500)), frequencies, geometries, and internal rotational barriers for 1-fluoropropane, 1,1-difluoropropane, 1,1,1-trifluoropropane, 1,2-difluoropropane, 1,1,2-trifluoropropane, 1,1,2,2-tetrafluoropropane, 1,1,1,2-tetrafluoropropane, and 1,1,1,2,2-pentafluoropropane are calculated using ab initio methods. Enthalpies of formation (ΔHf°298 in kcal/mol) for the above eight compounds are estimated using the G2MP2 composite calculation method and isodesmic reactions. Entropies (S°298 in cal mol-1 K-1) and heat capacities (Cp(T) in cal mol-1 K-1) are estimated using HF/6-31G(d) determined frequencies and MP2(full)/6-31G(d) determined geometries. ΔHf°298 for the above compounds are −67.37, −123.66, −183.09, −109.75, −164.68, −216.38, −221.57, and −271.14 kcal/mol, respectively. Rotational barriers are determined, and hindered internal rotational contributions for S°298 and Cp(T) are calculated using the rigid rotor harmonic oscillator approximation with direct integration over energy levels of the intramolecular rotation potential energy curve.