Ideal Gas Thermodynamic Properties of Propyl tert-Butyl Ethers from Density Functional Theory Results Combined with Experimental Data

Ideal gas thermodynamic properties, S ◦ (T ), C ◦ p(T ), H ◦ (T )−H ◦ (0), ΔfH ◦ (T ), and ΔfG ◦ (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 iInternal 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.