Thermal Studies on the Phase Transitions of p-n-Dodecyloxy and p-n-Tetradecyloxy Benzoic Acids.: (Part III)

Thermal properties of p-n-dodecyloxy and p-n-tetradecyloxy benzoic acids have been investigated using a differential scanning calorimeter. Heat capacities of thermally stable and metastable crystals of these acids were estimated and the effects of the paraffinic chain attached to the benzoic acid on the formation of a metastable crystalline state are discussed. It is suggested that the disorder of hydrogen bond configuration in associating carboxylic acids in pairs brings about the formation of a metastable crystal state for the alkoxy benzoic acids in general. Under the same conditions the mobile paraffinic chains control the modification of the hydrogen bond during the course of crystallization.