ROTATIONAL COHERENCE SPECTROSCOPY AND STRUCTURE OF PHENOL DIMER

Rotational coherence spectroscopy has been used to measure the rotational constants of four isotopomers of phenol dimer and a single isotopomer of p-cresol dimer. From the results of these measurements, together with spectroscopic results reported by others, a geometry for phenol dimer is deduced. The species is found to be bound by O-H ... O hydrogen bond. The orientation of the phenyl moieties is such that they make maximal contact consistent with the constraints imposed by the hydrogen bond and by the van der Waals radii of the atoms. This geometric feature is cited as evidence for the significance of aromatic-aromatic attraction in the intermolecular interaction between the phenols.