title: Entropy versus aromaticity in the conformational dynamics of aromatic rings.
abstract: Comparison of the results of Car-Parrinello molecular dynamics simulations of isolated benzene, pyrimidine and 1,2,4-triazine molecules reveals that the unusually low population of planar geometry of the benzene ring is caused by entropy effects despite its high aromaticity. The decrease in symmetry of the molecule results in smaller changes in entropy and Gibbs free energy due to out-of-plane deformations of the ring, leading to an increase in the population of planar geometry of the ring. This leads to differences in the topology of potential energy and Gibbs free energy surfaces.
authors.affiliation: Department of X-Ray Diffraction Studies and Quantum Chemistry, SSI "Institute for Single Crystals", National Academy of Science of Ukraine, 60 Lenina Ave., Kharkiv, 61001, Ukraine, shishkin@xray.isc.kharkov.com.
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Shishkin
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Dopieralski
authors.forename: Irina V
authors.initials: IV
authors.lastname: Omelchenko
authors.forename: Leonid
authors.initials: L
authors.lastname: Gorb
authors.forename: Zdzislaw
authors.initials: Z
authors.lastname: Latajka
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski