Chiral Solvent Structure around Chiral Molecules: Experimental and Theoretical Study

Molecular dynamics simulations of bromocamphor in n-hexane, CCCl₄, and CHCl₃ were performed at three temperatures to establish the distribution of the solvent molecules about the solute and to see how this changed with temperature. The results were used to calculate the solvent contribution to the circular dichroism (CD) of the solute at each temperature. The variation in experimental CD as a function of temperature was also measured for bromocamphor, dibromocamphor, camphor, and fenchone in n-hexane, CCCl₄, and CHC1₃. Since the intrinsic CD of the solute is essentially temperature independent, the variation in measured CD as a function of temperature could be attributed solely to the solvent-induced CD. The results of calculations and experiments were used to explain the chiral solvent distribution induced about itself by a chiral molecule. The observed effects were able to be explained in terms of pockets around the solute being occupied by the solvent and therefore creating a dissymmetric arrangement around the optically active carbonyl chromophore. This effect was found to be very temperature dependent. The magnitude of the solvent effect was found to depend upon the nature of the solute as well as the solvent.