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Ionic liquids have been highlighted for several applications that contribute to promote green chemistry and sustainability concepts in processes of gas capture, especially greenhouse gases such as CO2. This work aims to characterize ionic liquids, such as 1-alkyl-3-methylimidazolium chloride, via computational simulation. Molecular dynamics methods were used to obtain relevant thermophysical properties in the temperature range from 298.15K to 363.15K, which was compared to experimental data obtained from the literature in order to validate the molecular models and the force field. The quantum-mechanical calculations based on density functional theory (DFT) provided relevant information about the most stable molecular geometries of these compounds in their isolated and dimer forms. The results obtained from different computational methodologies elucidated the preferred position of chloride ions surrounding the imidazolium ring, as well as the stabilization of ionic pairs that form a three-dimensional structure. This work will guide future works in which it is intended to study gel formation, such as of ionic liquids and solvent mixtures, particularly water and short alcohols. [ABSTRACT FROM AUTHOR]

Sulfur hexafluoride (SF6), widely used as a thermal insulator and in electrical equipment, is a totally fluorinated gas, becoming a perennial compound in the atmosphere. Because it is a good absorber of infrared radiation, it is considered a greenhouse gas. In this work, through a theoretical computational study using the density functional theory (DFT), we determine geometry, binding energy and vibrational properties of the SF6 molecule. The results showed that this molecule has a high warming potential, with a wide range of absorption of infrared radiation within the atmospheric window. [ABSTRACT FROM AUTHOR]

A comparative theoretical study of reactivity of methanol, n-butyl alcohol, tert-butyl alcohol, phenol.p-nitrophenol and p-methylphenol acetylation, through the analysis of the corresponding reaction intermediates was carried out. The acetylation of alcohols is one of the most frequently used transformations in organic synthesis as it provides an efficient and inexpensive means for protecting hydroxyl group in a synthetic process. The activation energies and the reaction intermediates energies, were calculated with two levels of theory DFT (B3LYP) and MP2 combined with basis set 3-21G* and 6-31G*.The calculated values were compared with literature data. The methanol presented the higher reactivity in the acetylation reaction and the DFT/6-31G* method reported the lower energy values. [ABSTRACT FROM AUTHOR]

In this work, the computational study of the thermal decomposition of malonic acid is presented. It was followed by two mechanisms, at five temperatures, in gas phase and in aqueous solution. The calculations were carried out by means of the density functional theory. The rate constant of the reaction for the studied conditions was calculated with the Eyring-Polanyi equation. The results were compared with the reported experimental values. Another type of calculation performed were the natural bond orbitals. The results obtained allowed to discuss different aspects about the proposed reaction mechanisms. [ABSTRACT FROM AUTHOR]

The preparation of two coordination compounds of the general formula [M(OH2)2(NCS)2(nico)2] is provided, where nico = 3-pyridine carboxiamide and M = manganese(II) (A) and iron(II) (B). Compounds were characterized by spectroscopic techniques (IR and UV-vis) and by the monocrystal's X-ray diffraction. A and B electronic structures were analyzed by Density Functional Theory (DFT) and the semi-empirical Hamiltonian INDO/S, determining spin multiplicity of the fundamental state through investigations of energies of the autoconsistent energies and of the theoretical and experimental UV-vis electronic specters. Results reveal that spin multiplicities of compounds A and B are respectively S = 2 and S = 5/2. There was a good concordance between experimental specters and those obtained by molecular modeling. The above reinforces its use as an exploratory tool in the study of inorganic compounds and new materials. [ABSTRACT FROM AUTHOR]