comparision of conformation and vibrational properties of -C(O)S- and -C(O)O- compound

M. E. DEFONSI LESTARD; DIEGO M. GIL; M. E. TUTTOLOMONDO; A. BEN ALTABEF

Jena

Conferencia; ICORS2014 XXIV. International Conference on Raman Spectroscopie; 2014

Leibniz Institute of Photonic Technology (IPHT) together with the Institute of Physical Chemistry of the Friedrich Schiller University Jena (FSU) and the Abbe Center of Photonics

The functional group idea is useful to understand the chemistry of biological macromolecules. Atoms and functional groups possess characteristic and additive properties that in many cases exhibit a remarkable transferability between different molecules. Knowledge of the structural properties and conformational preference of simple molecules containing distinct functional groups is therefore of prime interest. As a follow up of studies for ?C(O)S? and?C(O)O? compounds in this work, a comparison is presented of conformational and vibrational properties of R1C(O)SR2 (R1= CF3, CH3 and R2=CH2CH3, CH3)1 and R1C(O)OR2 (R1= CF3, CCl3, CH3 and R2= CH3, CH2CH3, CH2CF3, SiCH3)2-5 which includes the use of vibrational spectroscopy ( FTIR- gas and liquid phase, Raman-liquid phase (Figure 1)) and quantum chemical calculations (B3LYP and MP2 methods). The behavior of hyperconjugative interactions with changing substituents and their relationship to vibrational properties is studied with the NBO program to understand how this group affects the change of substituents. Figure 2 presents the relationship between the anomeric effect LP S/O *C=O in ?C(O)S? and the ?C(O)O? compound. In this figure an increment can be observed in the anomeric effect LP O *C=O when the  C=O decreases, this effect being higher when the C=O goup is bonded to the more electronegative group for the ?C(O)O? compounds. For ?C(O)S? compounds the behavior is in the opposite direction, where an increase of the LP S *C=O anomeric effect increases the  C=O. It is important to note that the greater the difference in the environment electronegativity is, the higher is the interaction of energy LP S/O *C=O. Moreover, when the anomeric effect is higher, a strengthening of C-O/S bond is expected. This is reflected in an increment in the stretching frequencies of this mode.