Chemical Thermodynamics and Thermal Analysis最新文献

Atorvastatin calcium trihydrate (ACT) is a synthetic lipid-lowering agent whose thermal character remains largely unknown or else mischaracterized due to being called both “atorvastatin” and “atorvastatin form I” indiscriminately in the literature. Developing stable drugs, however, requires ensuring and thus understanding the reliable thermal behavior of trihydrate drugs, for pharmaceutical manufacturing can involve temperatures that might cause phase transition and/or the dehydration of the drugs, with implications for its physical characteristics, its chemical characteristics, and/or the pharmaceutical product's bioactivity. Against that background, in our study we investigated both a solid-state and thermal characterization of ACT via powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy (HSM), and ex situ variable temperature PXRD techniques, all as integral parts of drug development. DSC and TGA curves clarified ACT's thermal stability and dehydration, and the ACT sample was identified as Form I of the trihydrate, which remains stable until approximately 40 °C. DSC showed no significant changes during melting with different heating rates, while the TGA curve revealed the stepwise loss of water molecules following heating. Ex situ PXRD suggested no abrupt changes to the trihydrate's crystal lattice during the dehydration of the first two moles of water molecules. Moreover, HSM clearly showed a unique water loss event never before visualized. Last, HSM confirmed the drug's crystallinity, its crystal shape, and the presence of an isotropic liquid after continuous heating, which remained until cooling to room temperature.

The apparent molar volume$\left(V_{\varphi }\right)$ and apparent molar isentropic compressibility $\left(K_{\varphi ,s}\right)$ of ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG) in trisodium ethylenediaminetetraacetic acid solution (aqueous) have been estimated based on measured experiments values for both the density $(\rho$) and sound speed (s) at (288.15, 298.15, 308.15 and 318.15) K and 0.01 MPa as well. From the foundation in infinite dilution limiting apparent molar volumes $\left(V_{\varphi }^{{}^{\circ }}\right)$ and isentropic compressibility$\left(K_{\varphi ,s}^{{}^{\circ }}\right)$ its transfer properties $(\Delta V_{\varphi }^{{}^{\circ }}$, $\Delta K_{\varphi ,s}^{{}^{\circ }})$, expansibility coefficients${\left(\partial E_{\varphi }^{{}^{\circ }}/\partial T\right)}_P$, expansion coefficient ($\alpha$) and interactions coefficients $(V_{AB},K_{AB},V_{ABB},K_{ABB})$ the various interactions among glycols and EDTA in aqueous solution were investigated and addressed. Fourier transform infrared spectroscopy study had also been carried in binary solution.

This study delineates the empirical findings derived from the extraction of Sarsasapogenin from Amphipterygium Adstringens, commonly known as Cuachalalate, utilizing supercritical carbon dioxide (CO₂) as a solvent. The experiments were conducted within a temperature spectrum of 314 to 328.4 K and a pressure range of 8–22 MPa. The operational duration was set at 90 min with a CO₂ solvent flow rate oscillating between 40 and 50 mL/min. The equipment employed was predicated on the dynamic-analytical method. The extract´s qualitative determination was performed using a liquid chromatograph interfaced with a mass spectrometer (HPLC-MS). In contrast, the quantitative analysis was executed employing Ultraviolet Visible spectroscopy (UV–Vis) and Fourier Transform Infrared Spectroscopy (FTIR). Sarsasapogenin was identified as the representative compound in the Cuachalalate bark extract. The quantitative evaluations revealed that the maximum extract yield, amounting to 26.56 mg, was obtained under optimal operating conditions. Furthermore, this study investigated the influence of pressure and temperature variations on the extract´s yield.

This research presents a thermodynamic and acoustic investigation of the monosodium glutamate (MSG) food preservative in an aqueous solution. The addition of polyethylene glycol (PEG 400) and (PEG 600) as a solute is employed to create a ternary solution. The acoustic and volumetric parameters for the liquid mixture (water + monosodium glutamate + polyethylene glycol) at various temperatures (288.15 K, 298.15 K, 308.15 K, and 318.15 K) and constant pressure of 0.1 MPa. were determined using a range of monosodium glutamate concentrations [(0.01), (0.02), and (0.03) $\text{mol}.k{g}^{-1}].$In the experiment, a density and sound velocity measurement, the Anton Paar DSA 5000 M, was used. Many distinct thermodynamic variables, including partial molar transfer parameters and apparent and partial molar characteristics, are calculated from the experimental data. According to the McMillan-Mayer theory, the estimated derived parameters are then used to produce the pair-triplet coefficients and the first derivatives of the partial molar expansibilities. The results provide valuable insights into the MSG-PEG system's molecular interactions and thermodynamic behavior, offering potential applications for enhanced food preservation techniques in the food industry.

The importance of calorimetric data in elaboration of estimation methods of thermodynamic parameters is outlined. Four criteria for calorimeter classification are considered: (i) the parameter controlled by the instrument during the measurement, (ii) the way of taking over the heat accompanying the process, (iii) the method used in order the evaluate the value of the thermal effect and (iv) the procedure by which some reactants get in contact with the measuring part of the instrument. The progresses in the accuracy of the measurements and the extension of the applications of calorimetry during time have been evidenced.

Bond strengths are key values for the prediction of molecular behavior (reactivity, spontaneity, etc.). The values of bond strengths are often not directly experimental ones, but rather are calculated from experimental data. Also, transferability of bond strength values is a still discussed subject.

In this small communication several kinds of bond strengths and their transferability are addressed. Rearrangement enthalpies and apparent contradictions between their values and spontaneity of the process are analyzed. An alternative approach is proposed to explain these inconsistences for the case of ethane.

The energetics of formation and the phase transitions for isomeric methyl and ethyl methoxy‑benzoates were studied. The vapour pressures of methyl 2‑methoxy-benzoate and methyl 4‑methoxy-benzoate were measured by transpiration method. The high-precision combustion calorimetry was used to derive the liquid-phase enthalpy of formation of methyl 2‑methoxy-benzoate. The new results and the data available in the literature were critically evaluated using the structure-property correlations. Reliable correlations were established between the vaporisation enthalpies and the normal boiling temperatures as well as with the Kovats indices. Moreover, the validity of vaporisation enthalpies of alkyl methoxy‑benzoates was proved using structure-property relationships within families of structurally similar molecules. Mutual validation of the experimental and theoretical gas phase enthalpies of formation was performed using high-level quantum-chemical methods. The enthalpic contributions to the enthalpy of formation in the gas phase, resulting from the nearest and non-nearest neighbour interactions of the substituents in the benzene ring, were developed and used to quantify the intra-molecular hydrogen bond strength in the ortho-substituted species.

This article combines data from two previous reports together with new data dealing with the vaporization enthalpies and vapor pressures of a series of saturated and unsaturated fatty acid methyl ester(s) (FAME) by correlation gas chromatography. The work updates earlier results using newly proposed vaporization enthalpies for the saturated FAME used as standards in previous work. This update also provides some insight into the requirements necessary for appropriate column and standard selection for experiments using correlation gas chromatography. Vaporization enthalpies and vapor pressures for saturated FAME methyl heneicosanoate, methyl docosanoate, and methyl tetracosanoate are re-evaluated and together with proposed literature values for methyl tetradecanoate to methyl eicosanoate, are used to evaluate similar properties for a series of unsaturated fatty acid esters. Updated results on the vaporization enthalpies and vapor pressures of a number of unsaturated fatty acid methyl esters (FAME) found in marine oil are reported including several relatively reactive omega-3-polyunsaturated esters. Omega-3-FAME include methyl (9,12,15)Z-octadecatrienoate, methyl (5,8,11,14,17)Z-eicosapentaenoate, and methyl (4,7,10,13,16,19)Z-docosahexenoate among other unsaturated methyl esters. Also included in the study of the omega-3-unsaturated esters is the drug Vescepa®, ethyl (5,8,11,14,17)Z-eicosapentaenoate, a drug used to lower triglyceride levels.

Despite being one of the best-known families of organic compounds, the fact that hydrocarbons exhibit a rich variety of structures owing to branching, cyclization, and the presence of multiple bonds, means that many of their properties are yet to be determined accurately, or even at all. Among cyclic hydrocarbons, those with three-membered rings are particularly interesting because of their strain energy. In this paper, we report accurate calculations of the enthalpy of formation of three-membered carbocycles, whose experimental values have not been obtained by direct measurement of the heat of combustion. For this purpose, we used several accurate composite methods to obtain the gas-phase enthalpies of atomization and derived from them the gas-phase enthalpies of formation, using experimentally determined accurate values for the atoms. Moreover, to minimize the inaccuracy that can possibly arise in this procedure, we also used homodesmotic reactions designed to balance systematic errors in the geometric and electronic structure of some of the species. A careful analysis of the results shows that some of the indirectly derived values reported in the literature are far from the most accurate theoretical outcomes, and we suggest that these new ones should be adopted.

Applications and reports of unique properties displayed by layered double hydroxides (LDHs) are steadily increasing. Fundamental insight into LDH synthesis is essential to developing sustainable production processes, and this can be acquired through an improved understanding of their underlying thermochemistry. The collection of work presented introduces LDHs, describes essential terminology, and provides a review of currently available literature focused on modelling methods and measurement techniques used to describe and capture standard thermodynamic formation property data of LDHs. A table of standard thermodynamic formation property data of LDHs is also presented at the end of the review.