Di You-Ying

Low-temperature heat capacities and standard molar enthalpy of formation of 4-(2-aminoethyl)-phenol (C8H11NO)

This paper reports that low-temperature heat capacities of 4-(2-aminoethyl)-phenol (C8H11NO) are measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of heat capacities as a function of the temperature was fitted by the least square method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at the interval of 5 K. The energy equivalent, epsilon(calor), of the oxygen-bomb combustion calorimeter has been determined from 0.68 g of NIST 39i benzoic acid to be epsilon(calor)=(14674.69 +/- 17.49)J.K-1. The constant-volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen-bomb combustion calorimeter to be Delta U-c=-(32374.25 +/- 12.93)J.g(-1). The standard molar enthalpy of combustion for the compound was calculated to be Delta H-c(m)circle minus = -(4445.47 +/- 1.77) kJ . mol(-1) according to the definition of enthalpy of combustion and other thermodynamic principles. Finally, the standard molar enthalpy of formation of the compound was derived to be Delta H-f(m)circle minus(C8H11 NO,s) = -(274.68 +/- 2.06) kJ . mol(-1), in accordance with Hess law.

Synthesis, Characterization and Thermochemistry of the Hydrated Barium Nicotinate

A new compound. barium nicotinate trihydrate, wits synthesized by the method of room temperature solid phase synthesis and ball grinder. FTIR, chemical and elemental analyses, and X-ray powder diffraction techniques were applied to characterize the structure and composition of the complex. Low-temperature heat capacities of the solid coordination compound were measured by it precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A phase transition process occurred in the temperature range of 312-332 K in the heat capacity curve, and the peak temperature, molar enthalpy and entropy of the solid-to-solid phase transition of the complex were determined to be its follows: T-trs=(327.097+/-1.082) K, Delta H-trs(m)=(16.793+/-0.084) kJ center dot mol(-1) and Delta S-trs(m) =(51.340+/- 0.164) J center dot K-1 center dot mol(-1). The experimental values of the molar heat capacities in the temperature regions of 7 8-311 K and 333-400 K were respectively fitted to two polynomial equations. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature of 298.15 K were calculated and tabulated at an interval of 5 K. In accordance with Hess law, it thermochemical cycle was designed, the reaction enthalpy of the solid phase reaction was determined its Delta H-t(m)0 =-(84.12+/-0.38) kJ center dot mol(-1), and the standard molar enthalpy of formation of the complex was calculated as Delta H-f(m)0 [Ba(Nic)(2) center dot 3H(2)O(s)]=-(2115.13+/-1.90) kJ center dot mol(-1) by using an isoperibol solution-reaction calorimeter.

Studies on Thermal Decomposition Mechanism and Kinetics of Aspirin

The mechanism of thermal decomposition of aspirin was studied by both thermogravimetry and Mayer bond orders calculated by Cerius2 software. The parameters of thermal decomposition kinetics for aspirin, such as activation energy (E), reaction order (n) and frequency factor (A) were obtained by thermogravimetry. The kinetic equation of thermal decomposition of aspirin is expressed as:

Low-temperature heat capacities and standard molar enthalpy of formation of pyridine-2,6-dicarboxylic acid

This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78 K to 380 K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.

Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C11H17NO(s)

This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO(s) have been measured by a precision automated adiabatic calorimeter over the temperature range from T = 78 K to T = 400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T = 342–364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T = 78–342 K and T = 364–400 K were fitted to two polynomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO(s) relative to the standard reference temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T = 298.15K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.

Crystal structure and thermochemical properties of bis(1-octylammonium) tetrachlorochromate phase change materials

A new crystalline complex (C8H17NH3)2CdCl4(s) (abbreviated as C8Cd(s)) is synthesized by liquid phase reaction. The crystal structure and composition of the complex are determined by single crystal X-ray diffraction, chemical analysis, and elementary analysis. It is triclinic, the space group is P−1 and Z = 2. The lattice potential energy of the title complex is calculated to be UPOT (C8Cd(s))=978.83 kJmol−1 from crystallographic data. Low-temperature heat capacities of the complex are measured by using a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K. The temperature, molar enthalpy, and entropy of the phase transition for the complex are determined to be 307.3±0.15 K, 10.15±0.23 kJmol−1, and 33.05±0.78 JK−1mol−1 respectively for the endothermic peak. Two polynomial equations of the heat capacities each as a function of temperature are fitted by using the least-square method. Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials.