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Conformational Cooling Dynamics in Matrix-Isolated 1,3-Butanediol
Rosado, Mário T. S.; Jesus, António J. Lopes; Reva, Igor D.; Fausto, Rui; Redinha, José S.The complete conformational space of monomeric 1,3-butanediol has been characterized theoretically, and 73 unique stable conformers were found at the MP2/6-311++G(d,p) level. These were classified into nine families whose members share the same heavy atom backbone configurations and differ in the hydrogen atom orientations. The first and third most populated backbone families are governed by the formation of an...
Selective IR-induced isomerization of 1,2-dichloropropane isolated in xenon matrix
Olbert-Majkut, Adriana; Reva, Igor D.; Fausto, RuiThe conformations of monomeric 1,2-dichloropropane isolated in low temperature xenon matrix were characterized experimentally using FTIR spectroscopy. The interpretation of the experimental spectra was aided by ab initio MP2/6-311++G(3df,3pd) calculations. Relative energies of three structures, differing by the orientation of the Cl-C-C-Cl dihedral angle, fall within 0-6 kJ mol-1 range. The spectral signatures ...
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...
Photochemical alpha-Cleavage in Pyran-2-thione: Generation of Aldehyde-Thiokete...
Breda, Susana; Reva, Igor D.; Lapinski, Leszek; Fausto, RuiNo Abstract ; http://dx.doi.org/10.1002/cphc.200400539
First experimental evidence of the third conformer of glycolic acid: combined m...
Reva, Igor D.; Jarmelo, Susana; Lapinski, Leszek; Fausto, RuiThe FT-IR spectra of monomeric glycolic acid, GA, isolated in argon and xenon matrices (at 10 and 20 K) were studied, enabling identification of three different conformers of GA. The most stable SSC conformer involves a hydrogen bond between the carbonyl group and the hydrogen atom of the alcohol hydroxyl group. The minor GAC and AAT forms involve intramolecular hydrogen bonds between alcohol and carboxyl OH gr...
IR-Induced Photoisomerization of Glycolic Acid Isolated in Low-Temperature Iner...
Reva, Igor D.; Jarmelo, Susana; Lapinski, Leszek; Fausto, RuiGlycolic acid (HO−CH2−COOH) monomers isolated in low-temperature argon and krypton matrices were studied using FTIR spectroscopy. The most stable SSC conformer of the compound dominated in the matrices immediately after their deposition. Upon broadband infrared irradiation, two minor conformers (GAC and AAT) were photogenerated. No other forms of glycolic acid were populated, either thermally or photochemically...
Conformational Behavior of Cyanoacetic Acid: A Combined Matrix Isolation Fouri...
Reva, Igor D.; Stepanian, Stepan G.; Adamowicz, Ludwik; Fausto, RuiThis work reports the first experimental study of the cyanoacetic acid (CAA) monomer. Samples of CAA were isolated in low-temperature argon, krypton, and xenon matrixes and characterized using FTIR spectroscopy. Annealing experiments revealed the presence of different conformers in the matrixes. The direct interconversion of the gauche−cis (gc) into the cis−cis (cc) conformer was observed upon annealing of matr...
Combined FTIR Matrix Isolation and Ab Initio Studies of Pyruvic Acid: Proof fo...
Reva, Igor D.; Stepanian, Stepan G.; Adamowicz, Ludwik; Fausto, RuiThe molecular structure of pyruvic acid was investigated by matrix isolation FTIR spectroscopy, density functional theory (DFT), and ab initio calculations performed at the RHF, MP2, MP4(SDQ), and CCSD(T) levels of theory with the aug-cc-pVDZ basis set. In these calculations, the geometries of the three lowest energy conformers of pyruvic acid were fully optimized at the DFT/B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVD...
Conformational isomerism in methyl cyanoacetate: A combined matrix-isolation in...
Reva, Igor D.; Ilieva, Sonia V.; Fausto, RuiStudy of the conformational isomerism of methyl cyanoacetate (NCCH2COOCH3, MCA) aided for the first time by matrix-isolation infrared spectroscopy is reported. The conformational isomerization processes in MCA in the temperature range from 10 to 70 K were studied in detail in argon and xenon matrixes. During annealing of the matrixes direct interconversion of the gauche into the syn conformer has been registere...
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