Pressure and temperature Raman study of reorientational relaxation of propyne in hydrogen bonded complexes

A Raman band study of propyne in the liquid phase and in solutions with inert and active solvents as a function of temperature (−80 to+80 °C) and pressure (1–4000 bar) is reported. An increase of the reorientational correlation times τϑ with increasing pressure was found. It is shown that the theoretical correlation functions for diffusion-type models (the extended diffusion theory and the Fokker–Planck–Langevin friction theory) can reproduce the experimental correlation functions of propyne only in the absence of hydrogen bonding. It is also shown that a relatively free rotation of the propyne symmetry axis in acetone–propyne complexes takes place even at the highest pressures, and two simple pictures of the motion are proposed.