Flip-flops in fluorinated o-cresol

Ab initio geometry optimizations are used to investigate the side chain fluorinated cis o-cresols, HOC6H4CH3-nFn (n = 1, 2, and 3). The three ground states are found to contain hydrogen bonded hexagon, which may flip flop between two equivalent positions relative to the phenyl ring. In the cases n = 2 and n = 3 the activation energy for the flip-flop is about the same and less than 1 kJ/mol, whereas it is an order of magnitude higher for n = 1. The difference in activation energies is associated with the dynamics of the flip-flop and the stoichiometry of the cresol. (C) 2000 Elsevier Science B.V. All rights reserved.