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Structure of the 2-isopropylaminoethanol isolated molecule: Conformational anal...
Nunes, Sandra C. C.; Eusébio, M. Ermelinda S.; Jesus, A. J. Lopes; Rosado, Mário T. S.; Redinha, J. S.In this paper, a systematic exploration of all the possible conformers of 2-isopropylaminoethanol (2-IPAE) was carried out using the Density Functional Theory (B3LYP) and the 6-311++G(d,p) basis set. At this level, 66 unique conformers within a Gibbs energy range of ca. 31 kJ mol-1 were found in the potential energy surface and their geometrical and thermodynamic properties were determined and discussed. A sign...
Structure of Isolated 1,4-Butanediol: Combination of MP2 Calculations, NBO Anal...
Jesus, A. J. Lopes; Rosado, Mário T. S.; Reva, Igor; Fausto, Rui; Eusébio, M. Ermelinda S.; Redinha, J. S.Theoretical calculations at the MP2 level, NBO and AIM analysis, and matrix-isolation infrared spectroscopy have been used to investigate the structure of the isolated molecule of 1,4-butanediol (1,4-BDO). Sixty-five structures were found to be minima on the potential energy surface, and the three most stable forms are characterized by a folded backbone conformation leading to the formation of an intramolecular...
Solvation enthalpy and the thermodynamics of hydration of trans-cyclohexyl-1,4-...
Tomé, Luciana I. N.; Jesus, A. J. Lopes; Castro, R. A. Esteves de; Teixeira, M. Helena S. F.; Canotilho, João; Eusébio, M. Ermelinda S.The enthalpy of solution of trans-cyclohexyl-1,4-diamine and cis-cyclohexyl-1,2-diamine in water was determined by calorimetry. The enthalpy of hydration was determined from this quantity and from the enthalpy of sublimation/vaporization presented in another paper by the authors. Considering the solvation process resulting from cavity creation in the solvent and variation of solute conformation transfer steps, ...
Conformational study of isolated pindolol by HF, DFT and MP2 calculations
Nunes, Sandra C. C.; Jesus, A. J. Lopes; Rosado, Mário Túlio S.; Eusébio, M. Ermelinda S.In the present work a conformational analysis of pindolol, a beta-blocker, is performed using several computational methods, including HF, DFT (B3LYP) and MP2. The relative electronic energies as well as the relevant dihedral angles of the significant conformer geometries are reported. ; http://www.sciencedirect.com/science/article/B6TGT-4MH298S-1/1/026f88aa2cf86bb29b69a8f7cf4ac876
Conformational Study of Monomeric 2,3-Butanediols by Matrix-Isolation Infrared ...
Jesus, A. J. Lopes; Rosado, Mário T. S.; Reva, Igor; Fausto, Rui; Eusébio, M. Ermelinda; Redinha, J. S.The FT-IR spectra of two diastereomers of 2,3-butanediol, (R,S) and (S,S), isolated in low-temperature argon and xenon matrixes were studied, allowing the identification of two different conformers for each compound. These conformers were characterized by a ±gauche arrangement around the O−C−C−O dihedral angle, thus enabling the establishment of a very weak intramolecular hydrogen bond of the O···H−O type. No o...
Enthalpy of Sublimation in the Study of the Solid State of Organic Compounds. A...
Jesus, A. J. Lopes; Tomé, Luciana I. N.; Eusébio, M. Ermelinda; Redinha, J. S.The enthalpies of sublimation of erythritol and l-threitol have been determined at 298.15 K by calorimetry. The values obtained for the two diastereomers differ from one another by 17 kJ mol-1. An interpretation of these results is based on the decomposition of this thermodynamic property in a term coming from the intermolecular interactions of the molecules in the crystal (ΔintH°) and another one related with ...
Enthalpy of vaporisation of butanediol isomers
Eusébio, M. Ermelinda; Jesus, A. J. Lopes; Cruz, Mafalda S. C.; Leitão, M. Luísa P.; Redinha, J. SimõesThe enthalpies of vaporisation of isomers of butanediol were determined by calorimetric measurements. A Knudsen effusion cell was used for this purpose. ; http://www.sciencedirect.com/science/article/B6WHM-47K2P6J-2/1/6a970623f372c267e60917eff9f702c6
Molecular Structure of Butanediol Isomers in Gas and Liquid States: Combinatio...
Jesus, A. J. Lopes; Rosado, Mário T. S.; Leitão, M. Luísa P.; Redinha, José S.Density functional theory (Becke3LYP/6-311++G**) conformational analysis was carried out for all positional butanediol isomers. Taking into account the relative populations of the most stable conformers at 298.15 K, the weighted mean enthalpies of each butanediol isomer in the gas state were computed. Combining these results with the experimental values for the enthalpies of vaporization at 298.15 K, an estimat...
Enthalpy of solvation of butanediols in different solvents
Jesus, A. J. Lopes; Eusébio, M. Ermelinda; Redinha, J. S.; Leitão, M. L. P.The enthalpies of solution for 1,2-, 1,3-, 1,4- and 2,3-butanediol in water, formamide and dimethylsulphoxide were determined by calorimetry. From the results and data available in the literature for the enthalpy of vaporisation, the enthalpy of solvation was determined. The enthalpy of solvation was decomposed into two terms, cavity formation in the solvent to hold the solute and solute-solvent interaction. ;...
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