If a sample of the pure R enantiomer of a molecule has a specific rotation of - 40° and your mixture of that molecule has an 82% ee S, what is the observed specific rotation of your sample?

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Quizplus · Accepted Answer

% ee = (observed/specific) × 100.82 = (X/40) × 100; 82 = (100 X)/40; 82 × 40 = 100 X; 3280 = 100 X; X = 3280/100 = 32.8. Since the pure R rotates the polarized light counterclockwise or levorotatory (which is determined by the rotation being negative) and your mixture is predominately S, the observed rotation will be positive.

If a Sample of the Pure R Enantiomer of a Molecule