This project involves the study of the conformational analysis of several aminoacids as well as models of dipeptides (N-acetyl-R-N-methylamide: R=glycine, alanine, valine, phenylalanine and tyrosine), through NMR spectroscopy (H-1, C-13 and N-15) and by infrared spectroscopy and theoretical calculations of electronic structure. The theoretical calculations will be performed at ab initio MP2 and Density Functional Theory (DFT) levels with several basis sets and with zero-point corrections (ZPE), which will give the geometries and energies of the stable conformers in the isolated state and in solution with the IEFPCM solvation model. The infrared spectra in the fundamental carbonyl stretching frequency and in the first overtone, in several solvents, will be used to determine the conformer population ratios. A detailed H-1 and C-13 NMR study will show if the J(HH)geminal and vicinal couplings between the hydrogen atoms of the CH and CH2 groups follow the changes in conformer populations. Theoretical calculations of the carbonyl stretching frequencies and coupling constants J(HX)(X=H, C or N) together with experimental data, in several solvents, will be used for the determination of the conformer populations. The contributions of the intramolecular interactions of classical nature (steric and elctrostatic) and of quantum origem (Hyperconjugation) for the conformational stability of these compounds, besides the above data, will be evaluated by topological analysis through the Quantum Theory of Atoms in Molecules (QTAIM), Electronic Localization Function (ELF) and Natural Bond Orbitals (NBO). The results obtained by all these techniques will show which are the main factors responsible for the conformational prefernces of these important compounds. (AU)
Articles published in Agência FAPESP Newsletter about the research grant:
ROZADA, THIAGO C.;
GAUZE, GISELE F.;
ROSA, FERNANDA A.;
FAVARO, DENIZE C.;
PONTES, RODRIGO M.;
BASSO, ERNANI A.
The conformational analysis of 2-halocyclooctanones.
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY,
FEB 25 2015.
Web of Science Citations: 5.