Search

This is a systematic theoretical gas phase study of the gauche and trans conformers of 1-fluoro-2-haloethanes (FCH2CH2X, X=Cl, Br and I). The methods used are second order Møller-Plesset theory (MP2) and density functional theory (DFT). The basis set used is 6-311++(d,p) for all atoms except that 3-21G and CRENBL ECP are used for iodine atom. The functional used for DFT method is B3LYP. G2/MP2 calculation has also been carried out using MP2 optimised structure. The results indicate that unlike 1,2-difluoroethane, there is the absence of gauche effect and thus there is more preference for the trans conformer. The preference for the more stable trans conformer increases with increasing atomic size of the substituted halogen atom. The same trend is observed for energy difference between the gauche and trans conformers. The 1-fluoro-2-haloethanes have also been subjected to vibrational analysis. [ABSTRACT FROM AUTHOR]

The insertion reactions of singlet mono and dichlorocarbenes (1CHCl and 1CCl2) into primary, secondary and tertiary C-H bonds of methane, ethane, propane, n-butane and iso-butane have been investigated at ab initio (MP2) and DFT levels invoking 6-31g(d, p) basis set. Among the σ and π insertions into the said alkane C-H, both MP2 and DFT predict that the σ approach is slightly favoured over the π approach. For inverted σ approach the barrier heights have been found to be ca. 2 to 5 times that of the normal σ approach. [ABSTRACT FROM AUTHOR]