Yu-Xia Kong

n-Dodecyl­ammonium bromide monohydrate

In the title compound, C12H28N+·Br−·H2O, the ionic pairs formed by n-dodecylammonium cations and bromide anions are arranged into thick layers; these layers are linked in a nearly perpendicular fashion [the angle between the layers is 85.84 (5)°] by hydrogen-bonding interactions involving the water molecules. The methylene part of the alkyl chain in the cation adopts an all-trans conformation. In the crystal structure, molecules are linked by intermolecular N—H⋯Br, O—H⋯Br and N—H⋯O hydrogen bonds.

Thermochemistry on the Solid State Coordination Compounds M(Nic)2 · H2O(s) (M = Mn and Mg, Nic = Nicotinate)

Abstract Two novel solid state coordination compounds – manganese nicotinate monohydrate and magnesium nicotinate monohydrate were 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 these complexes. In accordance with Hess’ law, hermochemical cycles were designed, the enthalpy changes of the solid phase reactions of nicotinic acid with manganese acetate tetrahydrate and magnesium acetate tetrahydrate were determined as ΔrH0m,l = (39.66±0.36) kJ · mol–1 and ΔrH0m,2 = (40.73±0.17) kJ · mol–1 by use of an isoperibol solution-reaction calorimeter, respectively. The standard molar enthalpy of formation of the title complexes M(Nic)2 · H2O(s) were calculated as ΔfH0Mn(Nic)2·H2O = –(1165.01±2.01) kJ · mol–1 and ΔfH0Mg(Nic)2·H2O = –(1390.49±1.99) kJ · mol–1 by use of the enthalpies of dissolution and other auxiliary thermodynamic data. In addition, the values of the standard molar enthalpies of formation of M(Nic)2·H2O(s) (M = Mg, Mn, Zn) were compared, a law of change of [–ΔfH0Zn(Nic)2·H2O] < [–ΔfH0Mn(Nic)2·H2O] < [–ΔfH0Mg(Nic)2·H2O] can be obtained, and was in relation with the stability of the three monohydrated nicotinates.

Crystal Structure and Thermochemical Properties of 2-Pyrazine Carboxylate Lithium Monohydrate (Li(pyza)(H 2 O)) n (s)(pyza=2-Pyrazine Carboxylate)

A 2-pyrazine carboxylate lithium monohydrate [Li(pyza)(H2O)]n was synthesized in a mixed solution of redistilled water and anhydrous ethanol. X-Ray crystallography was applied to characterizing its crystal structure. Low temperature molar heat capacities were measured in a temperature range of from 78 K to 400 K with a precision automatic adiabatic calorimeter. Two polynomial equations of experimental molar heat capacity as a function of temperature were obtained by the least-squares method. The smoothed molar heat capacities and thermodynamic functions of the compound were calculated based on the fitted polynomial equations. In accordance with Hess’s law, a reasonable thermochemical cycle was designed based on the preparation reaction of the target compound. The standard molar enthalpies of dissolution for the reactants and products of the designed thermochemical reaction were measured by an isoperibol solution-reaction calorimeter, and the enthalpy change of the reaction was obtained, i.e., ΔrHmθ=-(30.084±0.329) kJ/mol. The standard molar enthalpy of the formation of the target compound was determined as

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

\Delta _f H_{m\{ [Li(pyza)(H_2 O)]_n (s)\} }^\theta = - (260.844 \pm 1.178)

Lattice potential energy and thermochemical properties of ethylenediamine dihydrochloride (C2H10N2Cl2)

kJ/mol based on the enthalpy change of the reaction and standard molar enthalpies of the formation of other reactants and products. In addition, UV-Vis spectroscopy and the data of the refractive indexes were used to confirm whether the designed Hess thermochemical cycle was reasonable and reliable.

Thermochemistry on ephedrine hydrochloride and N-methylephedrine hydrochloride

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.