Configurational Entropy in Chiral Solutions—Negative Entropy of Solvent Envelopes

Abstract: A homogeneous solution of a chiral substance is acquired with an overall asymmetry which is expressed by a specific rotation of a linearly polarized light. Such a solution, despite being at a complete equilibrium, stores configurational entropy in a form of negative entropy which can be nullified by mixing with a solution of the opposite enantiomer. This abundant, yet quite a specific case of inherent negative entropy, resides predominantly in the chiral configuration of the solvent envelopes surrounding the chiral centers. Heat release, amounting to several cal/mol, associated with the annulment of negative entropy in aqueous solutions of D- and L-amino acids, was recently documented by Shinitzky et al. [1]. This heat corresponds almost exclusively to TΔS stored in the solvent envelope upon adoption of a chiral configuration. Simple fundamental expressions which combine configurational entropy and information capacity in chiral solutions have been developed and were found to comply well with the observed heat release upon intermolecular racemization.