Conformation analysis of small molecules with <scp>PCILO</scp> methods

Abstract

Abstract The conformational potential of n ‐butane, ethyl methyl ether, n ‐propanol, methyl propyl ether, and 1,2‐dimethoxyethane was calculated with different PCILO algorithms as well as with ab‐initio SCF – LCAO – MO computations. Compared with ab‐initio calculations, the conformational potentials obtained by PCILO methods on the same geometries are too flat. In particular, the barrier at 0˚ (synperiplanar conformation) is much too low at the second‐ and third‐order level. This is mainly a consequence of the second‐order delocalization corrections. Since the PCILO algorithms are not capable of reproducing conformational potentials obtained from ab‐initio calculations, only qualitative predictions are possible.