Conformational analysis of the halomethyl cyclopropanes and the halosilyl cyclopropanes by molecular mechanics calculations

Abstract

Using non-bonding atom⋯atom interaction potentials derived from gas-phase data on haloalkanes, the torsional potentials in the molecules XH 2CC 3H 5 and XH 2SiC 3H 5 have been calculated. The molecules have stable gauche and syn conformations. Our calculations show that for FH 2CC 3H 5 syn is the conformer of lowest energy, while for the remaining XH 2CC 3H 5 molecules (X=Cl,Br,I) gauche is the low-energy form. In contrast to this, syn is the low-energy form of all XH 2SiC 3H 5 molecules X=(F,Cl,Br,I). The molecular mechanics results agree with the available observations on XH 2CC 3H 5 compounds (X=Cl,Br,I). Conformational energies, rotational barrier heights and torsional force constants have been calculated.