RESUMO
We report the observation of non-photochemical laser-induced nucleation (NPLIN) of sodium chlorate from its melt using nanosecond pulses of light at 1064 nm. The fraction of samples that nucleate is shown to depend linearly on the peak power density of the laser pulses. Remarkably, we observe that most samples are nucleated by the laser back into the enantiomorph (dextrorotatory or levorotatory) of the solid prior to melting. We do not observe a significant dependence on polarization of the light, and we put forward symmetry arguments that rule out an optical Kerr effect mechanism. Our observations of retention of chirality can be explained by decomposition of small amounts of the sodium chlorate to form sodium chloride, which provide cavities for retention of clusters of sodium chlorate even 18 °C above the melting point. These clusters remain sub-critical on cooling, but can be activated by NPLIN via an isotropic polarizability mechanism. We have developed a heterogeneous model of NPLIN in cavities, which reproduces the experimental data using simple physical data available for sodium chlorate.
RESUMO
Enantiomorphic symmetry breaking of stirred samples of molten sodium chlorate is demonstrated, revealing the unexpected involvement of an achiral solid phase. The results should stimulate future computational models of nucleation, including symmetry breaking, and have implications for mechanisms that invoke enantiomorphism in natural minerals to explain biohomochirality.
RESUMO
In the title compound, C(7)H(5)FO(2)·C(7)H(7)NO, a moderate-strength hydrogen bond is formed between the carboxyl group of one mol-ecule and the pyridine N atom of the other. The benzoic acid mol-ecule is observed to be disordered over two positions with the second orientation only 4% occupied. This disorder is also reflected in the presence of diffuse scattering in the diffraction pattern.
