Encontrados 6 documentos, a visualizar página 1 de 1
A Fragmentation study of di-acidic mycosporine-like amino acids in electrospray...
Cardozo,Karina H. M.; Vessecchi,Ricardo; Galembeck,Sérgio E.; Guaratini,Thais; Gates,Paul J.; Pinto,Ernani; Lopes,Norberto P.; Colepicolo,PioTwo mycosporine (MAAs), containing an extra acid function, were analyzed by nanospray and electrospray ionization tandem mass spectrometry. In contrast to the previous studies it is demonstrated that no significant characteristic methyl radical loss occurred in positive mode. The fragmentation pathway in negative mode was also proposed in this work, along with theoretical calculations to characterize the site o...
Aplicação da química quântica computacional no estudo de processos químicos env...
Vessecchi,Ricardo; Galembeck,Sérgio E.; Lopes,Norberto P.; Nascimento,Paulo G. B. D.; Crotti,Antônio E. M.The field of application of mass spectrometry (MS) has increased considerably due to the development of ionization techniques. Other factors that have stimulated the use of MS are the tandem mass spectrometry (MS/MS) and sequential mass spectrometry (MSn) techniques. However, the interpretation of the MS/MS and MSn data may lead to speculative conclusions. Thus, various quantum chemical methods have been applie...
Density, degeneracy, delocalization-based index of aromaticity (D3BIA)
Firme,Caio L.; Galembeck,Sergio E.; Antunes,O. A. C.; Esteves,Pierre M.Aromaticity has been exhaustedly discussed for several years and it remains as a misterious issue. In this work it is proposed a new index of aromaticity named density, degeneracy and delocalization-based index of aromaticity or simply D3BIA in an attempt to cast new insight and perspective over this theme. This index is based on AIM (atoms in molecules) theory and it is somewhat supported by SC (spin-coupled) ...
Efeitos de substituintes na ligação de hidrogênio do 3-hidroxipropenal
Rustici,Valéria C. F.; Caramori,Giovanni F.; Galembeck,Sérgio E.The effect of substituents on the energies and geometries of 3-hydroxypropenal was studied using the B3LYP/6-311++G(d,p) model. The hydrogen bond energies indicate that the strongest donors and the weakest acceptors present the highest and the weakest hydrogen bonds, respectively, indicating the validity of the Madsen RAHB model. Geometric parameters indicate that the intensity of the hydrogen bond is proportio...
Qual o sítio de reação? Um experimento computacional
Galembeck,Sérgio E.; Caramori,Giovanni F.A computational quantum chemistry experiment is described on the determination of the most reactive atom in a molecule for a reaction. The reaction studied was the S N2 of 4-(dimethylamino)pyridine and methyl iodide. Several indexes (HOMO coefficent, (c), charges, (q), nucleophilic softness, (s+), and Fukui index, (f+)) were employed to verify which correctly describe what nitrogen will react. The calculations ...
An electronic and vibrational study of the cyclopropenyl ion and its fluoroderi...
Galembeck, Sérgio E.; Fausto, RuiThis article presents the results of ab initio SCF-MO calculations on both the electronic structure and vibrational spectra of the cyclopropenyl cation (C3H3+) and its fluoroderivatives, C3H2F+, C3HF2+ and C3F3+. A very simple and unambiguous criterion for choosing the combination of diffuse and polarization functions which, together with the 6311G basis set, best describes the electron distribution in these io...
| Financiadores do RCAAP | |||||||
|
|
|
|
|
|
||