Low-Temperature Heat Capacities and Thermodynamic Properties of N-Benzyloxycarbonyl-l-3-phenylalanine (C17H17NO4)

Abstract

The heat capacities of N-benzyloxycarbonyl-L-3-phenylahmine were measured by means of a fully automated adiabatic calorimeter over the temperature range from (79 to 395) K. A solid liquid phase transition corresponding to the melting process was observed. The temperature, the molar enthalpy, and entropy of the phase transition were determined to be 358.799 K. 31.787 kJ.mol(-1), and 88.594 J.K-1.mol(-1), respectively. The mole fraction purity or the sample used in the adiabatic calorimetric study was determined to be 0.9830 according to the Van't Hoff equation. Two equations of temperature dependence for heat capacities in the solid and liquid state are presented. The thermodynamic functions. (H-T - H-298.15K) and (S-T - S-298.15K). were calculated based on the heat capacity data in the temperature range from (80 to 400) K with an interval of 5 K. The standard molar enthalpies of combustion have been determined to be Delta H-c(m)0(C17H17NO4, s) = -(8308.52 +/- 3.22) kJ.mol(-1), with a precision oxygen-bomb combustion calorimeter at T = 298.15 K. The standard molar enthalpy of formation of the compound has been derived from the enthalpy of combustion, Delta H-f(m)0(C17H17NO4, s) = -(815.05 +/- 0.67) kJ.mol(-1). The thermal stability of Me compound was further studied using TG, and DSC, and a possible mechanism for thermal decomposition was suggested.