Radiopolymerization of beta-pinene: a case of chiral amplification

beta(-)Pinene was treated with 7 radiation at three dose levels: 150, 300 and 600 kGy. The expected effect of radiation at these high doses was the partial racemization of the substrate as already observed in the case of other terpene monomers. Unexpectedly beta(-)pinene underwent a radiopolymerization reaction into a solid resin and into a dimer. The structure of the products was studied by FT-IR spectroscopy also in comparison to a reference beta(-)pinene resin prepared by cationic polymerization. A highly ordered structure was found in the case of the radiopolymer in comparison to the resin from cationic polymerization. Polarimetric measurements have shown astonishing enhancement in the optical activity of the radiopolymer and radiodimer in comparison to the starting optical activity of the beta(-)pinene monomer. The results have been discussed in terms of amplification of chirality caused by gamma radiation and the implications of this fact on the mechanism of chiral amplification on prebiotic molecules