Solid state M(2-MeO-BP) 2 compounds, where M stands for bivalent alkali earth metal ions (Mg, Ca, Sr and Ba) and 2-MeO-BP is 2-methoxybenzylidenepyruvate, have been synthesized.Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, elemental analysis and complexometry, were used to investigate these compounds.The dehydration of magnesium, strontium and barium compounds occurs in a single step, while for calcium compound the dehydration occurs in two steps.The thermal decomposition of the anhydrous compounds occurs with the formation of carbonate as intermediate, except for the magnesium compound.The results also provided information about the composition, coordination mode, thermal behavior and thermal decomposition of isolated compounds.
: The neodymium complex with the ligand norfloxacin was synthesized in the solid state. Characterization and thermal behavior of the compounds were performed employing X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and Simultaneous Thermogravimetry/Derivate Thermogravimetric-Differential Thermal Analysis (TG/DTG-DTA). From the TG/DTG-DTA curves, it was possible to determine the minimum formula ([Nd(Nor)3]6H2O), thermal stability and thermal decomposition steps. XRD showed that the complex was obtained with low crystallinity and analysis of the main bands of the IR spectrum it was possible to suggest the probable sites of coordination of the ligand to the neodymium ion.
1UFGD Univ Federal da Grande Dourados, Faculdade de Ciências Exatas e Tecnologia Departamento de Química, , P.O. Box 364, 79.804-970, Dourados – MS – Brazil. 2UNESP Univ Estadual Paulista, Instituto de Química de Araraquara Departamento de Química Geral e Inorgânica, P.O. Box 355, 14801-970, Araraquara – SP – Brazil. 3UNESP Univ Estadual Paulista, Faculdade de Ciências Farmacêuticas, 14800-903, Araraquara – SP – Brazil. 4UTFPR Univ Tecnológica Federal do Paraná Departamento de Química, P.O. Box 135, 86036-370, Londrina – PR – Brazil. 5 UNIFAL -Univ Federal de Alfenas Instituto de Química, 37130-000, Alfenas – MG – Brazil.
The thermal behaviour of amphiphilic systems involving (5-pentyl)trimethylammonium and dodecyl aldehyde-modified chitosans was studied. These amphiphilic chitosan derivatives were synthesized and characterized by 1HNMR and ATR-FTIR spectroscopies. Thermogravimetry (TGA) and differential scanning calorimetry (DSC) were used to determine their properties. It was found that the modification of the chitosan structure affects directly its thermal properties. The temperature at which water is released from the compounds showed that when adding the hydrophilic substituent water originally bound to an -NH2 group will bind to a less stronger >NH group requiring lower temperatures to be released. The addition of the hydrophobic C12 substituent confers a more micelle-like structure to the compound, leaving some water molecules within the core of the micelle, making its release more difficult. The decomposition peak observed around 300 °C, corresponding to the decomposition of the chitosan rings, is split in two peaks when adding the substituents, indicating the influence of the substituents on the ring decomposition reactions.
Paracetamol ( acetaminophen , N -acetyl- p- aminophenol ) is an antipyretic analgesic that has anti -inflammatory effect and is widely used in Brazil . This work was made use of Thermogravimetry ( TG ) and differential scanning calorimetry ( DSC ) to determine the activation energy and purity of pharmaceutical commercial forms of reference, generic and similar containing the active principle paracetamol . The Ozawa method was applied for the activation energy using thermogravimetric curves in three heating rates ( 5 , 10 and 20 ° C min - 1 ) . The results showed an average activation energy for the thermal decomposition evaluated between 87.2 and 103.7 kJ mol -1 . The Van't Hoff equation applied to the paracetamol fusion event observed in the DSC curves showed 99.5 , 99.3 and 99.6 % purity for the reference samples , and like generic , respectively.
