On the polymorphism of solid cyclohexanol by adiabatic calorimetry and far infrared methods

Abstract

Adiabatic calorimetry and FIR spectroscopy were used to get a better understanding of the polymorphism of solid cyclohexanol. On the basis of calorimetric measurements performed in the temperature range from 170 K to 320 K and the entropy balance calculation, the monotropic set of phases II and III was confirmed. The conditions in which different phases can be grown and the reversibility of the particular phase transition were checked. Two different ways for obtaining phase III, one passing through an intermediate metastable phase MS, were demonstrated by both methods. The influence of the thermal treatment on the apparent stability of phase III was discussed. In addition to the previously reported IR observation of the transformation from phase III to II, the same monotropic transition was visualized in the calorimetric measurement Nous avons utilise la calorimetrie adiabatique et la spectroscopie dans l'infrarouge lointain afin de mieux comprendre le polymorphisme du cyclohexanol solide. Nous avons pu confirmer le systeme monotropique des phases II et III en nous basant sur les mesures calorimetriques effectuees entre 170 et 320 K et le bilan de l'entropie. Nous avons verifie les conditions de croissance de chacune des phases et les reversibilites des transitions de phases. Nous avons trouve deux facons d'atteindre la phase III dont une necessite le passage par la phase intermediaire metastable MS. A cote de l'observation de la transition entre phases III et II par methodes infrarouges, la technique calorimetrique nous a aussi permis d'observer la meme transition monotropique