Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Polish Journal of Chemistry

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: rotational isomerism

Sortuj według:

Ogranicz wyniki do:

Effect of the Dielectric Medium on the Conformational Behaviour of Methyl 3-Nitrobenzoate

Konopacka A., Kalenik J., Pawełka Z.

Polish Journal of Chemistry

2006

Vol. 80, nr 9

1583-1592

Conformational analyses of methyl 3-nitrobenzoate (MNB) was performed, employing DFT, MP2, and semi-empirical quantum-chemical calculations, as well as classical methods based on atomic charge and dipole moment approximations. Properties such as the relative energies of the O-NO2 trans and O-NO2 cis isomers, their populations and dipole moments, all in vacuum, were considered first. Then the conformational trans cis equilibrium was quantitatively established by dipole moment measurements in solvents of dielectric permittivities between 2.016 and 10.34. Different approaches, based on continuum-dielectric and MSAmodels were explored to explain the contribution of the electrostatic interaction to the standard Gibbs energy change delta G° of the trans cis transformation in MNB in solution.

Theoretical (DFT in Vacuo) Studies on the Structure of 2-(_-Aminoethyl)-pyridine - an Agonist of the Histamine H1Receptor. Comparison with Experiment (FT-IR in Apolar Solvent)

Raczyńska E., Darowska M., Rudka T.

Polish Journal of Chemistry

2003

Vol. 77 / nr 11

1529-1546

Preliminary quantum-chemical calculations (DFT) were performed for 2-(_-aminoethyl)- pyridine (AEP). In calculations, rotational isomerism around the single C-C and C-N bonds of the chain aminoethyl group in AEPwas considered. Nine stable conformations (four trans and five gauche) with similar Gibbs energies were found. For all of them, vibrational frequencies were calculated at the DFT(B3LYP)/6-31G* level. Infrared (FT-IR) spectra were recorded in apolar solvent (CCl4) for various concentrations of AEP, and compared with those found by computations. The comparison shows that in apolar CCl4 solution AEP exists as a mixture of different conformers. Analysis of the experimental stretching NH and CH vibrations, and the bending in-plane NH vibrations suggests that all nine conformers of AEP can be present in CCl4 solution.