RAMAN-STUDY OF CONFORMATIONAL EQUILIBRIUM IN PLASTIC SOLID DODECAMETHYLCYCLOHEXASILANE SI(6)ME(12)

The temperature dependence of the Raman spectrum of solid dodecamethyl cyclohexasilane Si(6)Me(12) has been studied in the temperature interv al 20-235 degrees C. At 72 degrees C the substance undergoes a phase t ransition of an <<order--disorder>> type, from the ordered crystalline modification to the plastic mesophase with isotropic molecular reorie ntations. This phase transition is accompanied by the appearance of a conformational equilibrium in the solid state. An analogous equilibriu m is also observed in a benzene solution, where the concentration of t he second conformer is already noticeable at 6 degrees C.