Raman spectroscopic study of the formation of fossil resin analogues

Abstract

The purpose of this work is to provide spectroscopic evidence of possible chemical pathways that took place in the formation of fossil resins Class I. The natural polymerization process is mimicked in the laboratory using pure communic acids (terpene derivatives) as reactants, which were subjected to controlled temperature treatment. We shall focus here on the trans-, cis- and iso-/ mirceo- communic acid isomers, and the temperature-induced reactivity is discussed on the basis of the different arrangements of the conjugated double-bonds moieties in the monomeric units. Transformations starting at 130, 90 and 127 °C, for trans-, cis- and iso-communic acids, respectively, led to the formation of intermediate products. The whole process was followed and analyzed by micro-Raman spectroscopy. The absence of several Raman signatures suggests conjugation loss in the side-chain of these intermediate compounds. With increasing temperature, the intermediate products suffer additional maturation reactions to form the final fossil resin analogues object of this work.