amount of major enantiomer - amount of minor enantiomer
amount of major enantiomer + amount of minor enantiomer
In this case, amount of major enantiomer = 4 and amount of minor enantiomer = 1.
Therefore, ee = 4-1
= 3 =
0.6 = 60%
4+1 5
The optical purity is defined as:
specific rotation of sample
specific rotation of an enantiomerically pure sample
Therefore, optical purity =
5.5 = 0.458
= 45.8%
12
These two values are not numerically equal, and this suggest that the compound undergoes intermolecular aggregation resulting in the formation of dimers, trimers, tetramers etc. The observed specific rotation will then be the average of the specific rotation of each species present, and this may be different to the enantiomeric excess of the sample.
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