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A study of the structure of the pindolol based on infrared spectroscopy and nat...
Castro, Ricardo A. E.; Canotilho, João; Nunes, Sandra C. C.; Eusébio, M. Ermelinda S.; Redinha, J. Simõeshttp://www.sciencedirect.com/science/article/B6VNG-4V1KMV6-1/2/37bbea9fe5940f0b4f9225e65592559b
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...
The structure of betaxolol from single crystal X-ray diffraction and natural bo...
Canotilho, João; Castro, Ricardo A. E.; Rosado, Mário T. S.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.; Redinha, J. SimõesThe structure of betaxolol obtained from ethanol:water solution was studied by X-ray diffraction. The geometrical parameters needed to define the structure are tabulated. The X-ray data show the existence of two conformers in the unit cell differing only in the conformation of the cyclopropylmethoxy fragment. Differences in the bond lengths angles and dihedral between both conformations are observed. The cyclop...
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...
Infrared spectroscopy of racemic and enantiomeric forms of atenolol
Castro, R. A. Esteves de; Canotilho, João; Barbosa, Rui M.; Redinha, J. SimõesThe molecular structure of conformational isomorphs given by X-ray diffraction for racemic and enantiomeric atenolol were optimized at the HF/6-31G* level of theory and the infrared spectra of the structure were calculated. These spectra are used to characterize the differences between the various atenolol conformers. ; http://www.sciencedirect.com/science/article/B6VNG-4M3R2CM-5/1/b10f1bad0cbecc44994eccae4c...
Molecular structure of mono- and 1,2-aminoderivatives of cyclohexane: Steric st...
Tomé, Luciana I. N.; Rosado, Mário T. S.; Eusébio, M. Ermelinda S.; Redinha, J. S.The conformational study of cyclohexylamine and 1,2-cyclohexylamine derivatives was performed. The potential energy surface of every compound was calculated at B3LYP/6-31G(d) and the conformational energy minima were further optimized at B3LYP/aug-cc-pVDZ level of theory. The geometrical parameters and the electronic energy of each conformer were determined. The internal energy, enthalpy, entropy, Gibbs energy ...
Conformational Isomorphism of Organic Crystals: Racemic and Homochiral Atenolol
Castro, R. A. Esteves de; Canotilho, João; Barbosa, Rui M.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.; Redinha, J. SimõesX-ray diffraction analysis of (R,S)- and S-atenolol crystalline forms was performed. The crystals studied were grown from evaporation of an ethanol/water solution. (R,S)-Atenolol crystallizes in the centrosymmetric space group C2/c, and S-atenolol crystallizes in a noncentrosymmetric space group C2. There is one symmetry independent molecule in (R,S)-atenolol crystals and two symmetry independent molecules in S...
Infrared study of the acidic and basic forms of betaxolol
Canotilho, João; Castro, R. A. Esteves de; Helena, M.; Teixeira, S. F.; Leitão, M. Luísa P.; Redinha, J. SimõesBetaxolol and its respective hydrochloride salt were studied in solution by computational calculations and infrared spectroscopy. The solution molecular conformations were taken to be the same as those exhibited by the compounds in the solid state given by X-ray diffraction and calculated after full geometry optimization by ab initio Hartree-Fock methods using the 6-31G(d) basis set. Infrared spectra of carbon ...
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...
Stepwise conformational cooling towards a single isomeric state in the four int...
Reva, Igor D.; Jesus, António J. Lopes; Rosado, Mário T. S.; Fausto, Rui; Eusébio, M. Ermelinda; Redinha, J. S.The present work explores the possibilities of the matrix isolation technique in the structural characterisation of highly flexible molecules. To date, most studies of this type were carried out on molecules with three or less internal degrees of freedom and a few (less than 10) possible conformations. The molecule of 1,2-butanediol has four conformationally relevant three-fold rotational axes, which can result...
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