Ultraviolet–visible spectroscopy of stereoisomers explained

Ultraviolet–visible spectroscopy (UV–vis) can distinguish between enantiomers by showing a distinct Cotton effect for each isomer. UV–vis spectroscopy sees only chromophores, so other molecules must be prepared for analysis by chemical addition of a chromophore such as anthracene. Two methods are reported: the octant rule and the exciton chirality method.^[1]

The octant rule was introduced in 1961 by William Moffitt, R. B. Woodward, A. Moscowitz, William Klyne and Carl Djerassi.^{[2] [3] [4]} This empirical rule allows the prediction of the sign of the Cotton effect by analysing relative orientation of substituents in three dimensions and in this way the absolute configuration of an enantiomer.

See also

• NMR spectroscopy of stereoisomers

Notes and References

1. .
2. Structure and the Optical Rotatory Dispersion of Saturated Ketones William Moffitt, R. B. Woodward, A. Moscowitz, W. Klyne, Carl Djerassi J. Am. Chem. Soc., 1961, 83 (19), pp 4013–4018
3. The octant rule: Its place in organic stereochemistry William S. Murphy J. Chem. Educ., 1975, 52 (12), p 774 Publication Date: December 1975
4. A Simple Computer-Aided Three-Dimensional Molecular Modeling for the Octant Rule Yinan Kang, Fu-An Kang J. Chem. Educ., 2011, 88 (4), p 420