Can Enantiomorphic Crystals Like Quartz Play a Role in the Origin of Homochirality on Earth?

Abstract

This communication reviews the possible actions of enantiomorphic crystals on the surface of Earth as sources of homochirality of organic compounds. The discovery of asymmetric adsorption and asymmetric catalysis involving optically active quartz crystals has led some authors to conclude that this source of asymmetry played an important role as a source of homochirality in nature, a concept that later proved erroneous. Moreover, data regarding the preponderance in nature of l-quartz crystals have been used to confirm calculations of the parity violation energy difference (PVED) for l-quartz and, hence, to explain the prevalence of L-amino acids and D-sugars in living matter. As discussed here, quartz and other enantiomorphs such as sodium chlorate can produce chiral intermediates active in autocatalytical processes. Our most recent compilation of the literature, however, reveals that the distribution of d- and l-quartz crystals at the surface of the Earth when all possible locations are included is quite random. Although quartz can serve as an effective asymmetric inductor in autocatalytic processes, it cannot be the source of homochirality of living matter because of the random occurrence of the two types of enantiomorphs. The calculations of PVED values for quartz therefore lack a sound physical basis.