The Enantiomeric Excess (ee) Calculator finds the ee, enantiomeric ratio (er), and optical purity of your chiral mixture — just pick your calculation method and enter either R and S enantiomer percentages, peak areas, or your observed and specific rotation, and it determines the dominant enantiomer with a full purity breakdown.
Enantiomeric Excess (ee)
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Major Enantiomer
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Enantiomeric Ratio (er)
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Optical Purity
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Enantiomeric excess (ee) measures the optical purity of a chiral compound, expressing how much one enantiomer dominates over the other. It ranges from 0% (racemic mixture) to 100% (pure enantiomer) and is crucial in pharmaceutical and chemical synthesis where chirality affects biological activity.
The formula is ee(%) = |R - S|/(R + S) × 100, where R and S are the percentages of each enantiomer. For example, if you have 75% R and 25% S enantiomers, the ee would be |75-25|/100 × 100 = 50%.
Yes, peak areas from chiral HPLC or GC are directly proportional to enantiomer concentrations. Simply use the peak areas as if they were percentages in the ee calculation formula.
Enantiomeric excess can be calculated from optical rotation using ee(%) ≈ (αobs/αpure) × 100, where αobs is the observed rotation and αpure is the specific rotation of the pure enantiomer. This assumes a linear relationship between optical rotation and ee.
The enantiomeric ratio (er) expresses the proportion of major to minor enantiomer as a simple ratio. For example, 90% ee corresponds to an er of approximately 95:5, making it easier to visualize the enantiomer distribution.
0% ee indicates a racemic mixture where both enantiomers are present in equal amounts (50:50 ratio). This occurs naturally in many synthetic reactions that don't use chiral catalysts or reagents.
Optical rotation measurements can be less accurate than chromatographic methods because they assume a linear relationship between rotation and ee, which may not always hold. HPLC or GC with chiral columns generally provide more reliable ee determinations.