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Matrix-Isolated Diglycolic Anhydride: Vibrational Spectra and Photochemical Rea...
Jarmelo, S.; Reva, I. D.; Lapinski, L.; Nowak, M. J.; Fausto, R.The structure of diglycolic anhydride (1,4-dioxane-2,6-dione; DGAn) isolated in a low-temperature argon matrix at 10 K was studied by means of FTIR spectroscopy. Interpretation of the experimental vibrational spectrum was assisted by theoretical calculations at the DFT(B3LYP)/aug-cc-pVTZ level. The optimized structure of the isolated DGAn molecule adopts an envelope conformation, which was found to resemble clo...
Molecular Structure, Infrared Spectrum, and Photochemistry of Squaric Acid Dime...
Breda, S.; Reva, I.; Lapinski, L.; Fausto, R.Squaric acid dimethyl ester (C6O4H6; 3,4-dimethoxycyclobut-3-ene-1,2-dione; DCD) was studied by matrix isolation infrared spectroscopy and by density functional theory (B3LYP) and ab initio (MP2) calculations with the 6-31++G(d,p) and 6-311++G(d,p) basis sets. Three conformers of the compound were theoretically predicted. The two most stable conformers were identified in low-temperature argon matrixes and the e...
Photochemical Ring-Opening and Intramolecular Hydrogen Shift Reactions in Sulfu...
Breda, S.; Reva, I.; Lapinski, L.; Cristiano, M. L. S.; Frija, L.; Fausto, R.A combined matrix isolation FTIR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the photochemistry of sulfur analogues of α-pyrone [2H-thiopyran-2-one (TP) and 2H-pyran-2-thione (PT)] was carried out. The vibrational spectra of monomers of the compounds isolated in low-temperature argon matrixes were studied experimentally and assigned completely on the basis of theoretical calculations. UV irradiation (λ > ...
UV-induced photochemistry of methyl coumalate (methyl 2-pyrone-5-carboxylate) i...
Reva, I. D.; Nowak, M. J.; Lapinski, L.; Fausto, R.Photochemical transformations of methyl coumalate have been studied by matrix-isolation technique. Two photoreactions were induced by UV ([lambda] > 295 nm) light: isomerisation to the Dewar form and [alpha]-bond cleavage leading to the open-ring aldehyde-ketene. The first photoprocess was found to be strongly dominating. Experimental evidence of photoreversibility of both photoisomerisation processes has been ...
Infrared spectra of pyrazine, pyrimidine and pyridazine in solid argon
Breda, S.; Reva, I. D.; Lapinski, L.; Nowak, M. J.; Fausto, R.The vibrational spectra of monomeric diazines (pyrazine, pyrimidine and pyridazine) isolated in solid argon and of the neat crystalline phase of these compounds, at 10 K, are reported and discussed. Full assignment of the spectra is presented, providing evidence that the assignments of several bands previously undertaken for the compounds under other experimental conditions (e.g., gas phase, neat liquid or solu...
Preferred Conformers and Photochemical (λ > 200 nm) Reactivity of Serine and 3,...
Jarmelo, S.; Lapinski, L.; Nowak, M. J.; Carey, P. R.; Fausto, R.A systematic investigation of the conformational potential energy surface of neutral serine [HOCH2CHNH2COOH] and 3,3-dideutero-serine [HOCD2CHNH2COOH] was undertaken, revealing the existence of 61 different minima. The structures and vibrational spectra of the most stable conformers, which were estimated to have relative energies within 7 kJ mol-1 and account for ca. 93% of the total conformational population a...
Matrix-Isolation FTIR Spectroscopy of Benzil: Probing the Flexibility of the C...
Lopes, S.; Gómez-Zavaglia, A.; Lapinski, L.; Chattopadhyay, N.; Fausto, R.The infrared spectrum and conformational flexibility of benzil, (C6H5CO)2, are studied by matrix-isolation FTIR spectroscopy, supported by DFT calculations. It is shown that the low-frequency (ca. 25 cm-1), large-amplitude torsion around the C−C central bond strongly affects the structural and spectroscopic properties exhibited by the compound. The equilibrium conformational distribution of molecules with diffe...
Matrix isolation FTIR and theoretical study of a-pyrone
Breda, S.; Reva, I.; Lapinski, L.; Fausto, R.A combined matrix isolation FTIR and molecular orbital study on the photochemistry of alpha-pyrone (AP) was undertaken. The most efficient of the observed photoprocesses was the Norrish type I, ring opening reaction leading to conjugated ketene. Upon irradiation of matrix isolated AP with UV (λ>285 nm) light, rapid formation of Z isomers of the aldehyde–ketene was observed. After a few minutes of irradiation th...
4,6-Dimethyl-α-pyrone: a matrix isolation study of the photochemical generation...
Breda, S.; Lapinski, L.; Reva, I.; Fausto, R.A combined matrix isolation and molecular orbital study of the vibrational spectra and photochemistry of 4,6-dimethyl-α-pyrone (DMAP) was undertaken. Two types of photoreactions: ring opening leading to conjugated ketene and valence isomerization to the Dewar form (1,5-dimethyl-2-oxa-3-oxobicyclo[2.2.0]hex-5-ene; DOOBH), occurred upon UV (λ>315 nm) irradiation. The latter reaction was efficient, whereas aldehyd...
Low temperature matrix-isolation and solid state vibrational spectra of 5-chlor...
Bugalho, Susana C. S.; Serra, A. C.; Lapinski, L.; Cristiano, Maria Lurdes Santos; Fausto, R.The vibrational spectra of 5-chlorotetrazole (CN4HCl) isolated in an argon matrix (T ¼ 8.5 K) and in the solid state (at room temperature) were studied. The infrared spectrum of monomers of 5-chlorotetrazole isolated in an argon matrix agrees well with the spectrum predicted theoretically (DFT(B3LYP)/6-31G*) for the 2Htautomer of the compound. The bands assigned to the 1H-tautomer appear in the experimental spe...
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