Thermochemistry of 4-HOC6H4COR (R = H, CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, and n-C6H13) compounds

• Enthalpies of vaporization/sublimation of 4-HOC6H4COR compounds were measured by Calvet microcalorimetry.
• ΔfHm° (g) of 4-HOC6H4COR compounds were obtained from W1-F12 and CCSD(T)-F12 ab initio calculations.
• The corresponding ΔfHm° (cr) were derived from the experimental ΔvapHm° or ΔsubHm° data and the computational ΔfHm° (g) results.
• The ΔsubHm° values show an approximately additive increase with the number of carbon atoms in the alkyl side chain.
• An excellent linear correlation was found between the ΔfHm° (g) values and the number of carbon atoms in the alkyl side chain.

The thermochemistry of 4-HOC6H4COR (R = H, CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, and n-C6H13) compounds was investigated using enthalpy of vaporization/sublimation measurements by Calvet-drop microcalorimetry and W1-F12 and CCSD(T)-F12 ab initio calculations. Based on the obtained results, standard (p° = 1 bar) molar enthalpies of formation in the solid, ΔfHmo(cr), and gaseous, ΔfHmo(g), states, at T = 298.15 K, could be derived for the complete series of compounds. An excellent linear correlation was found when the ΔfHmo(g) values were plotted as a function of the number of carbon atoms in the alkyl side chain (nc), with a CH2 increment of 21.8 ± 0.2 kJ·mol−1. Despite the differences in molecular packing between the crystalline 4-HOC6H4COR compounds, approximate additivity of their cohesive energies (as measured by the standard molar enthalpy of sublimation) with nc was also noted, the CH2 increment being 6.6 ± 0.6 kJ·mol−1.