The molecular mechanisms of rotational-isomeric and structural relaxat
ions in liquid o- and p-fluorotoluene are considered on the basis of a
coustic spectra. It was experimentally established that, near the free
zing point, o- and p-fluorotoluene has two conformal isomers. The enth
alpies and rates of transition governed by the hindered rotation of th
e methyl group are computed. In the investigated temperature range (18
3-493 K), the structural relaxation may be described by the reactions
of breaking and formation of weak intermolecular bonds. The minimum in
the temperature dependence of the structural relaxation time is deter
mined by the interrelation of the rate constants of the forward and re
verse reactions. The thermodynamic and kinetic parameters of the struc
tural reconstruction are calculated.