Regiosseletividade de reações N-/O- Nitroso Aldol: um estudo DFT das reações de Nitrosobenzeno com Morfilina e Pirrolidina
Aromatic C-nitroso compounds have been widely studied because of their versatility. Investigations of these compounds can be found in several areas of scientific knowledge. The nitroso group (R-NO) acts ambivalently, that is, as nucleophile and electrophile. Aldo N-/O-Nitroso reactions have been...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/27406 |
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| Resumo: | Aromatic C-nitroso compounds have been widely studied because of their
versatility. Investigations of these compounds can be found in several areas of
scientific knowledge. The nitroso group (R-NO) acts ambivalently, that is, as
nucleophile and electrophile. Aldo N-/O-Nitroso reactions have been explored, in
particular, using nitrosobenzene (PhNO) for new synthetic routes. The investigation
of the reactive processes in computational chemistry steps, essentially, by
calculations of electronic energy, in which information is obtained on the energies
and the relative structural changes of the species involved in the chemical reactions.
In this work, computational methods were used to understand how mechanical
processes occur: 1-morpholine-1-cyclohexene reacting with nitrosobenzene and 1-
pyrrolidine-1-cyclohexene also reacting with nitrosobenzene. All stationary points of
reaction were calculated using the DFT method M06-2X/6-31+G(d,p). After this
step, the single points were performed with B2PLYP-D3/6-311+G(2d,p) method, for
obtain more accurate results. The results showed that the reaction process goes
through three stages: transition states 1 (TS1), zwitterion intermediates and
transition states 2 (TS2). Analogously to the reactions of Diels-Alder, the reactions
studied present endo and exo isomerism. It led to eight possible confomation for the
TS1 of each reaction, as well as for the intermediates. In TS2, however, only four
structures were obtained for reaction with 1-morpholinecyclohexene, where as
structures with exo isomeria would change to endo isomerism. However, with
pyrrolidine, two conformations were obtained. Furthermore, for the reaction of 1-
morpholinecyclohexene, a reaction mechanism was presented which corroborates
with experimental studies. For the 1-pyrrolidinecyclohexene, the method used was
not effective to be in agreement with experimental results. Thus, this work provides
a perspective for elucidation of the aldol N- / O-Nitrosoreaction. |
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