Role of latent heat in chiral symmetry breaking transition in the crystallization of 1,1′-binaphthyl

The influence of latent heat dissipated by the crystallization of 1,1′binaphthyl in its supercooled molten state on the chiral symmetry breaking transition was investigated. Temperature change in the crystallization system was monitored by infrared thermocamera. Temperature rise due to the dissipation of latent heat in the growing front of polycrystalline aggregate was about 2° C in an unstirred crystallization system. The melting point of racemic mixture and racemic compound of 1,1′-binaphthyl is 145° C and 158° C, respectively. The latent heat generated by the crystallization could thus change the crystallization behavior when the initial temperature of the melt was slightly lower than 145° C. The temperature change in both unstirred and stirred crystallization systems was monitored. In the stirred crystallization system, even in the case when the initial temperature of the melt was about 2° C lower than 145° C, the temperature rose by about 4° C immediately after the onset of crystallization. This indicates that the role of stirring as the critical parameter for the chiral symmetry breaking transition is not only to clone the chiral crystals but also to enhance the dissipation of latent heat due to secondary nucleation.