Low-temperature heat capacities and thermodynamic properties of ethyl 4-dimethylaminobenzoate (C11H15NO2)

Abstract

Molar heat capacities of ethyl 4-dimethylaminobenzoate were measured by a high precision automated adiabatic calorimeter over the temperature range from 79 to 397 K. The melting temperature, the molar enthalpy and entropy of fusion were determined to be (336.818 ± 0.017) K, (20.761 ± 0.345) kJ mol−1 and (61.64 ± 1.03) J K−1 mol−1. It has a great potential in the use of the substance as solid–liquid phase change material based on large enthalpy of solid–liquid phase transition and moderate melting temperature. The thermodynamic functions (HT−H298.15 K) and (ST−S298.15 K) were calculated in the temperature range from 80 to 400 K with the interval of 5 K. The mass fraction purity of the sample was determined to be (1−N) = 0.99514 (mol fraction) by the fractional melting method. The constant-volume energy and standard molar enthalpy of combustion were determined, ΔcU (C11H15NO2, s) = −(6,161.73 ± 5.19) kJ mol−1 and Δc\( H_{\text{m}}^{0} \) (C11H15NO2, s) = −(6,167.31 ± 5.19) kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T = 298.15 K. At last, the standard molar enthalpy of formation was derived, Δf\( H_{\text{m}}^{0} \) (C11H15NO2, s) = −(305.03 ± 6.92) kJ mol−1.