PROTON-TRANSFER IN THE SOLID-STATE - THERMODYNAMIC PARAMETERS FROM AN X-RAY STUDY IN THE TEMPERATURE-RANGE 20-293 K

From single-crystal X-ray diffraction data measured at 293, 240, 147 and 20 K, values of DELTA-H = 1.6 +/- 0.6 kcal mol-1 and DELTA-S = 4.5 +/- 2.2 cal mol-1 K-1 are obtained for the tautomeric equilibrium between the p-quinonemethide and the o-quinone forms of citrinin. A correlation between bond lengths and equilibrium composition at different temperatures is presented.