Zastosowanie metod chemii kwantowej DO interpretacji efektu podstawnikowego W wybranych układach cyklicznych zawierających grupę nitrową
Abstract
This study presents an investigation of substituent effect (SE) in physical term, using quantum chemistry modeling. Substituent effect in series of meta(1,3-) and para(1,4)-X- substituted nitro derivatives of cyclic systems: benzene (BEN), cyclohexa-1,3-diene (CHD) and para-bicyclo[2,2,2]octane (BCO), with 16 different substituents (X = NMe2, NH2, OH, OMe, CH3, H, F, Cl, CF3, CN, CHO, COMe, CONH2 , COOH, NO2, NO), was analyzed. To describe the SE, quantum chemistry models: cSAR (charge of the substituent active region), SESE (substituent effect stabilization energy) and π/ Electron Donor/Acceptor indices (pEDA/sEDA) were used. Delocalization of πelectron in the transmitting moiety (BEN, butadiene fragment of the CHD) was described by index HOMA and pEDA parameter for transmitter [pEDA(R)]. The novelty of the analysis presented here is its description of SE by the population of electrons in sigma and pi orbitals for both the nitro group and the ring for derivatives of para- and meta-substituted nitrobenzene and para-type cyclohexadi-1,3-ene systems. Application of quantum chemical modeling made it possible to compare the substituent effects observed in systems differ the nature of transmitter. It was observed that strength of substituent effect decrease in a sequence: olefinic CHD, aromatic BEN and aliphatic BCO. The obtained results clearly document different nature of intramolecular interactions between NO2 group and X in BEN and CHD systems (coexistence of resonance and…
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