Yu-Pu Liu

Crystal structures, lattice potential energies, and thermochemical properties of crystalline compounds (1-C(n)H(2n+1)NH3)2ZnCl4(s) (n = 8, 10, 12, and 13).

As part of our ongoing project involving the study of (1-C(n)H(2n+1)NH(3))(2)MCl(4)(s) (where M is a divalent metal ion and n = 8-18), we have synthesized the compounds (1-C(n)H(2n+1)NH(3))(2)ZnCl(4)(s) (n = 8, 10, 12, and 13), and the details of the structures are reported herein. All of the compounds were crystallized in the monoclinic form with the space group P2(1)/n for (1-C(8)H(17)NH(3))(2)ZnCl(4)(s), P21/c for (1-C(10)H(21)NH(3))(2)ZnCl(4)(s), P2(1)/c for (1-C(12)H(25)NH(3))(2)ZnCl(4)(s), and P2(1)/m for (1-C(13)H(27)NH(3))(2)ZnCl(4)(s). The lattice potential energies and ionic volumes of the cations and the common anion of the title compounds were obtained from crystallographic data. Molar enthalpies of dissolution of the four compounds at various molalities were measured at 298.15 K in the double-distilled water. According to Pitzers theory, molar enthalpies of dissolution of the title compounds at infinite dilution were obtained. Finally, using the values of molar enthalpies of dissolution at infinite dilution (Δ(s)H(m)(∞)) and other auxiliary thermodynamic data, the enthalpy change of the dissociation of [ZnCl(4)](2-)(g) for the reaction [ZnCl(4)](2-)(g)→ Zn(2+)(g) + 4Cl(-)(g) was obtained, and then the hydration enthalpies of cations were calculated by designing a thermochemical cycle.

Investigation on phase transitions of 1-decylammonium hydrochloride as the potential thermal energy storage material

1-Decylammonium hydrochloride was synthesized by the method of liquid phase synthesis. Chemical analysis, elemental analysis, and X-ray single crystal diffraction techniques were applied to characterize its composition and structure. Low-temperature heat capacities of the compounds were measured with a precision automated adiabatic calorimeter over the temperature range from 78 to 380 K. Three solid–solid phase transitions have been observed at the peak temperatures of 307.52 ± 0.13, 325.02 ± 0.19, and 327.26 ± 0.07 K. The molar enthalpies and entropies of three phase transitions were determined based on the analysis of heat capacity curves. Experimental molar heat capacities were fitted to two polynomial equations of the heat capacities as a function of temperature by least square method. 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 based on the fitted polynomials.

Crystal Structure and Solid–Solid Phase Transition of 1-Dodecylamine Hydrobromide

Abstract 1-dodecylamine hydrobromide was synthesized. The crystal structure of the compound was determined by X-ray crystallography. Low-temperature heat capacities of the title compound were measured by an adiabatic calorimeter over the temperature range from 78 to 390 K. Three solid–solid phase transitions were observed at the peak temperatures of (329.278±0.234), (337.805±0.326), and (347.371±0.154) K. The molar enthalpies and entropies of the three phase transitions of the substance were calculated based on the analysis of heat capacity curves. Experimental values of heat capacities for the title compound were fitted to two polynomial equations. Three solid–solid phase transitions and a melting process of 1-dodecylamine hydrobromide were verified by DSC technique. In addition, the reversibility and repeatability of the three phase transitions were discussed.

Lattice potential energy and standard molar enthalpy in the formation of 1-dodecylamine hydrobromide （1-C12H25NH3.Br） （s）＊

This paper reports that 1-dodecylamine hydrobromide (1-C12H25NH3Br)(s) has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3Br and the ionic volume and radius of the 1-C12H25NH3+ cation are obtained from the crystallographic data and other auxiliary thermodynamic data. The constant-volume energy of combustion of 1-C12H25NH3Br(s) is measured to be ΔcUmo(1-C12H25NH3Br, s) = −(7369.03±3.28) kJmol−1 by means of an RBC-II precision rotating-bomb combustion calorimeter at T = (298.15±0.001) K. The standard molar enthalpy of combustion of the compound is derived to be ΔcHmo(1-C12H25NH3Br, s) = −(7384.52±3.28) kJmol−1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be ΔfHmo(1-C12H25NH3Br, s)=−(1317.86±3.67) kJmol−1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.