Cyclohexyl chloride, bromide and cyclohexanone show two absorptions which, by comparison with the single absorption of o-dichlorobenzene in poly(styrene) are recognized as arising from an intra-molecular (chair-chair) configurational change and the whole-molecule reorientation. For thianthrene and its congeners only a single absorption was found, but one of unusual sharpness for dipole absorptions in a polymer matrix. The temperature dependence of the τ's gave activation parameters. In diphenylene dioxide and phenoxathiin the ΔH(act) values scarcely differed from zero, implying a quasi-resonant character for the intra-molecular (butterfly flapping) change in those instances. Fluorenone was studied as a model rigid molecule comparable with the thianthrene structure. The poly(styrene) matrix data are summarized as the Eyring rate parameters ΔHE in kJ mol–1: ΔSE in J deg–1 mol–1.[graphic ommitted]