Heat capacity and thermodynamic properties of pyrimethanil myristic salt (C26H41N3O2)

Pyrimethanil myristic salt was synthesized and its heat capacities were measured with an automated adiabatic calorimeter over the temperature range from T = (79 to 360) K. The melting point, molar enthalpy, Delta(fus)H(m) and entropy, Delta(fus)S(m), of fusion of this compound were determined to be (321.84 +/- 0.05) K, (56.53 +/- 0.03) kJ . mol(-1) and (175.64 +/- 0.05) J . mol(-1) . K-1, respectively. The purity of the compound was calculated to be 98.99 mol% by using the fractional melting technique. The thermodynamic functions relative to the reference temperature, T = 298.15 K, were calculated based on the heat capacity measurements in the temperature ranges from T = (80 to 360) K. The TG-DTG results demonstrate that the mass loss of the sample takes place in one step with the maximum rate at T = 500 K, which was caused by evaporation of the sample. (C) 2004 Elsevier Ltd. All rights reserved.

Calorimetric study and thermal analysis of crystalline nicotinic acid

As one primary component of Vitamin B-3, 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 T-trs = 451.4 K, a solid-to-liquid transition at T-fus = 509.1 K and a thermal decomposition at T-d = 538.8 K were found through the DSC and TG-DTG techniques. The molar enthalpies of these transitions were determined to be Delta(trs)H(m =) 0.81 kJ mol(-1), Delta(fus)H(m) 27.57 kJ mol(-1) and Delta(d)H(m) = 62.38 kJ mol(-1), respectively, by the integrals of the peak areas of the DSC curves.

Thermodynamic study of ibuprofen by adiabatic calorimetry and thermal analysis

Molar heat capacities of ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 400 K. The polynomial functions of C-p,C-m (J K-1 mol(-1)) versus T were established on the heat capacity measurements by means of the least fitting square method. The functions are as follows: for solid ibuprofen, at the temperature range of 79.105 K less than or equal to T less than or equal to 333.297 K, C-p,C-m = 144.27 + 77.046X + 3.5171X(2) + 10.925X(3) + 11.224X(4), where X = (T - 206.201)/127.096; for liquid ibuprofen, at the temperature range of 353.406 K less than or equal to T less than or equal to 378.785 K, C-p,C-m = 325.79 + 8.9696X - 1.6073X(2) - 1.5145 X-3, where X = (T - 366.095)/12.690. A fusion transition at T = 348.02 K was found from the C-p-T curve. The molar enthalpy and entropy of the fusion transition were determined to be 26.65 kJ mol(-1) and 76.58 J mol(-1) K-1, respectively. The thermodynamic functions on the base of the reference temperature of 298.15 K, (H-T - H-298.15) and (S-T - S-298.15), were derived. Thermal characteristic of ibuprofen was studied by thermo-gravimetric analysis (TG-DTG) and differential scanning calorimeter (DSC). The temperature of fusion, the molar enthalpy and entropy of fusion obtained by DSC were well consistent with those obtained by adiabatic calorimeter. The evaporation process of ibuprofen was investigated further by TG and DTG, and the activation energy of the evaporation process was determined to be 80.3 +/- 1.4 kJ mol(-1). (C) 2003 Elsevier B.V. All rights reserved.

Low-temperature heat capacity and thermodynamic properties of crystalline carboxin (C12H13NO2S)

Carboxin was synthesized and its heat capacities were measured with an automated adiabatic calorimeter over the temperature range from 79 to 380K. The melting point, molar enthalpy (Delta(fus)H(m)) and entropy (Delta(fus)S(m)) of fusion of this compound were determined to be 365.29 +/- 0.06K, 28.193 +/- 0.09 kJ mol(-1) and 77.180 +/- 0.02 J mol(-1) K-1, respectively. The purity of the compound was determined to be 99.55 mol% by using the fractional melting technique. The thermodynamic functions relative to the reference temperature (298.15 K) were calculated based on the heat capacity measurements in the temperature range between 80 and 360 K. The thermal stability of the compound was further investigated by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The DSC curve indicates that the sample starts to decompose at ca. 290degreesC with the peak temperature at 292.7degreesC. The TG-DTG results demonstrate the maximum mass loss rate occurs at 293degreesC corresponding to the maximum decomposition rate. (C) 2003 Elsevier B.V All rights reserved.

Calorimetric study and thermal analysis of berberine sulphate

The heat capacities of berberine sulphate [(C20H18NO4)(2)SO4.3H(2)O] were measured from 80 to 390 K by means of an automated adiabatic calorimeter. Smoothed heat capacities,{H-T-H-298.15} and {S-T-S-298.15} were calculated. The loss of crystalline water started at about 339.3+/-0.2 K, and its peak temperature was 365.8+/-0.6 K. The peak temperature of decomposition for berberine sulphate was at about 391.4+/-0.4 K by DSC curve. TG-DTG analysis of this material was carried out in temperature range from 310 to 970 K. TG and DSC curves show that there is no melting in the whole heating process.

Synthesis and thermo-decomposition mechanism of rare earth complexes with phenylacetic acid

Rare earth complexes with phenylacetic acid (LnL(3) . nH(2)O, Ln is Ce, Nd, Pr, Ho, Er, Yb and Y, L is phenylacetate, n = 1-2) were prepared and characterized by elemental analysis, IR spectroscopy, chemical analysis, and X-ray crystal structure. The mechanism of thermal decomposition of the complexes was studied by means of TG-DTG, DTA and DSC. The activation energy and enthalpy change for the dehydration and melting processes were determined.

CRYSTAL STRUCTURE AND THERMAL ANALYSIS OF ERBIUM COMPLEX WITH BENZENE ACETIC ACID

The crystal structure of erbium (III) complex of benzene acetic acid is reported. The complex crystallizes in the monoclinic space group P2(1)/a with a = 0,9008(3)nm, b=1.4242(5) nm, c=1.8437(7) nm, beta=98.80(3)degrees, V = 2.337(1) nm(3), Z = 4. The mechanism of thermal decomposition of complex has been studied by TG-DTG-DTA. The activation energy for dehydration reaction has been calculated by Freeman Carroll method. The enthalpy change for dehydration and phase change process has been determined.

Er_2((PhCH_2COO)_6)·4H_2O的结构及热分析

用X-射线四圆衍射仪测定了Er_2(PhCH_2COO)_6·4H_2O的晶体结构。配合物属于单斜晶系,空间群为P2_1/α,晶胞参数:α=0.9008(3)nm,b=1.4243(5)nm,c=1.8437(7)nm,β=98.80(3)°,V=2.337(1)nm~3,Z=4.采用TG-DTG-DTA研究了配合物的热分解过程,确定了热分解机理。采用Freeman-Carroll方法计算了配合物脱水过程的活化能和反应级数。用DSC测定了配合物脱水,熔化过程的焓变。

一种新型稀土苯甲酸铽配合物的合成、表征及其晶体结构

本文报道一种新型稀土苯甲酸配合物,[Tb(C_7H_5O_2)_3(C_7H_6O_2)(H_2O)]_2的合成。用元素分析、DTA、TG、DTG和IR光谱对其性质进行了表征,并测定了其晶体结构。晶体属三斜晶系,空间群为P1,Z=1。晶胞参数为:a=9.148(1),b=11.460(2),c=13.506(2)A;α=112.76(1),β=91.83(1),γ=91.99(1)°;V=1303.3(4)A~3。稀土离子形成九配位的单帽正方反棱柱型配合物,稍有崎变。

铕和铽与3,4-呋喃二甲酸双核配合物的合成、表征及其晶体结构

本文首次合成了铕(Ⅲ)和铽(Ⅲ)与3,4-呋喃二甲酸配合物,研究了它们的IR、DTA、TG、DTG和荧光光谱等性质,并完成了单晶的晶体分析。结果表明,配合物为〔Ln·HL_2(H_2O)_2〕_2·2H_2O(Ln=Eu(Ⅲ),Tb(Ⅲ);H_2L=3,4-呋喃二甲酸),属单斜晶系,P2/c空间群,Z=2,晶胞参数对铕和铽配合物分别为α=10.842(1),10.801(4);b=8.725(2),8.664(2);c=16.366(4),16.308(6)A;β=93.50(1),93.67(3)°;V=1545.3(5),1523.0(8)A~3。

Nickel(II) and copper(II) complexes containing 2-(2-(5-substitued isoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione ligands: Synthesis, spectral and thermal characterizations

Two new hydrazone chelating ligands, 2-(2-(5-methylisoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (HL1) and 2-(2-(5-tert-butylisoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane- 1,3-dione (HL2), and their nickel(II) and copper(II) complexes were synthesized using the procedure of diazotization, coupling and metallization. Their structures were postulated based on elemental analysis, H-1 NMR, ESI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films of these complexes on K9 glass substrates were prepared using spin-coating and their absorption properties were evaluated. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential thermogravimetry (DTG). Different thermodynamic and kinetic parameters namely activation energy (E