The heat capacities of N-(tert-butoxycarbonyl)-l-phenylalanine (abbreviated to NTBLP in this article), as an important chemical intermediates used to synthesize proteins and polypeptides, were measured by means of a fully automated adiabatic calorimeter over the temperature range from 78 to 350 K. The measured experimental heat capacities were fitted to a polynomial equation as a function of temperature. The thermodynamic functions, HT − H298.15K and ST − S298.15K, were calculated based on the heat capacity polynomial equation in the temperature range of (80–350 K) with an interval of 5 K. The thermal stability of the compound was further studied using TG and DSC analyses; a possible mechanism for thermal decomposition of the compound was suggested.
Authors:M.-H. Wang, Z.-C. Tan, Q. Shi, L.-X. Sun, and T. Zhang
heat capacities of 2-benzoylpyridine were measured with an automated adiabatic
calorimeter over the temperature range from 80 to 340 K. The melting point,
molar enthalpy, ΔfusHm,
and entropy, ΔfusSm,
of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03
kJ mol–1 and 66.07±0.05 J mol–1
K–1, respectively. The purity of the compound
was calculated to be 99.60 mol% by using the fractional melting technique.
The thermodynamic functions (HT–H298.15) and (ST–S298.15) were calculated based
on the heat capacity measurements in the temperature range of 80–340
K with an interval of 5 K. The thermal properties of the compound were further
investigated by differential scanning calorimetry (DSC). From the DSC curve,
the temperature corresponding to the maximum evaporation rate, the molar enthalpy
and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2
kJ mol–1 and 92.2±0.4 J K–1
mol–1, respectively, under the experimental
Authors:S. Wang, Z. Tan, Y. Di, F. Xu, M. Wang, L. Sun, and T. Zhang
As one primary component of Vitamin B3, nicotinic acid [pyridine 3-carboxylic acid] was synthesized, and calorimetric study and thermal analysis for this compound
were performed. The low-temperature heat capacity of nicotinic acid was measured with a precise automated adiabatic calorimeter
over the temperature rang from 79 to 368 K. No thermal anomaly or phase transition was observed in this temperature range.
A solid-to-solid transition at Ttrs=451.4 K, a solid-to-liquid transition at Tfus=509.1 K and a thermal decomposition at Td=538.8 K were found through the DSC and TG-DTG techniques. The molar enthalpies of these transitions were determined to be
ΔtrsHm=0.81 kJ mol-1, ΔfusHm=27.57 kJ mol-1 and ΔdHm=62.38 kJ mol-1, respectively, by the integrals of the peak areas of the DSC curves.