Hydrogen Bonding-Induced Circular Dichroism HBICD

2 Hydrogen Bonding-Induced Circular Dichroism (HBICD) 

In methanol, the extinction of the absorption at 241 nm is less than 40 % of the value in isopentane with little change on lowering the temperature. In isopentane, the extinction drops significantly to the value found in methanol when the temperature is lowered. The data on the temperature-dependent CD in methanol can be interpreted on the basis of a temperature-dependent equilibrium between two chiral species. The change of the rotatory strength appears to be AG° = —2.0 KJ mol-1. This phenomenon is interpreted by the assumption that the cis-conformer about the C(6)-C(7) bond is favored in methanol and, at lower temperatures, in isopentane. 

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