Ideal gas thermodynamic properties of propyl tert-butyl ethers from density functional theory results combined with experimental data

Ideal gas thermodynamic properties, Sdegrees(T), C(p)degrees(T), Hdegrees(T)-Hdegrees(0), Delta(f)Hdegrees(T), and DeltafGdegrees(T), are obtained on the basis of density functional B3LYP/6-31G(d,p) and B3LYP/6-311 + G(3df,2p) calculations for two propyl tert-butyl ethers. All torsional motions about C-C and C-O bonds were treated as hindered internal rotations using the independent-rotor model. An empirical approximation was assumed to account for the effect of the coupling of rotor potentials. The correction for rotor-rotor coupling was found by fitting to entropy values determined from calorimetric measurements. Enthalpies of formation were calculated using isodesmic reactions.