| Abstract [eng] |
In this work two newly synthesized molecules, 1-fluor-1-methyl-silacyclopentane and 1-fluor-1-chlormethyl-silacyclopentane, were analyzed to determine the effect of different radicals on conformations of a silacyclopentane ring. Using a combination of theoretical calculations and experimental vibrational spectroscopy methods (IR and Raman) several things have been determined. Firstly, the presence of a Si atom in a cyclopentane ring has a profound effect on the conformation of the ring – in the case of cyclopentane the most stable conformer is the envelope conformer, while for a silacyclopentane ring it is the half-chair conformer. Secondly, the presence of radicals also has an effect on molecular structure. 1-fluor-1-methyl-silacyclopentane posesses only one stable conformer, the axial confomer, due to the preference of the methyl group to occupy a pseudo-equatorial position that decreases the overall steric strain. 1-fluor-1-chlormethyl-silacyclopentane on the other hand has two stable conformers (axial and equatorial) with ΔH = 0.52 kJ/mol, the relatively small energy difference implies that these conformers are constantly changing between each other. Two conformers exist due to the interactions between the halogen atoms and the silacyclopentane ring, as well as repelling forces between the halogen atoms themselves. |
