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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...
Structure and vibrational spectra of -hydroxy isobutyric acid in the crystallin...
Jarmelo, Susana; Fausto, RuiInfrared spectra of monomeric -hydroxy isobutyric acid (HIBA) isolated in argon, krypton and xenon matrixes (at 8 K) are reported. It is shown that in all the studied matrixes HIBA exists preferentially as the intramolecularly H-bonded SsC conformer, where the HOCC, OCCO and OCOH dihedrals are 0°. In addition to the SsC form, two higher energy conformers (AaT and GskC) could be observed experimentally for the f...
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate
Jarmelo, Susana; Maria, Teresa M. R.; Leitão, Maria Luísa P.; Fausto, RuiThe low temperature crystalline and glassy phases of methyl -hydroxy-isobutyrate (MHib) were identified and characterized structurally by differential scanning calorimetry, IR and Raman spectroscopy and molecular modeling. Within the temperature range 13–171 K, MHib exists as a glassy state, where individual molecules may assume the two conformational states previously observed for this compound isolated in an ...
Structural and vibrational characterization of methyl glycolate in the low temp...
Jarmelo, Susana; Maria, Teresa M. R.; Leitão, Maria Luísa P.; Fausto, RuiThe low temperature phases of methyl glycolate (MGly) were identified and characterized structurally by differential scanning calorimetry, infrared and Raman spectroscopies and molecular modeling. Within the temperature range 13–273 K, MGly may exist in three solid phases. A crystalline phase (I) can be formed from the liquid upon slow cooling [Tonset=222–227 K] or from the low temperature glassy state resultin...
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