A chemist finds that the addition of (+)-epinephrine to the catalytic reduction of butan-2-one(Figure 5-16) gives a product that is slightly optically active, with a specific rotation of +0.45°.Calculate the percentages of (+)-butan-2-ol and (-)-butan-2-ol formed in this reaction.
Solution 13P :
Observed specific rotation of butan-2-ol = +0.45°.
Percentages of (+)-butan-2-ol and (-)-butan-2-ol formed in this reaction = ?
The rotation of pure butan-2-ol = +13.5 %
We know formula for optical purity :
Optical purity(o.p) = 100 %
Hence , o.p for butan-2-ol = 100 %
= 3.33 %
Therefore, the o.p of butan-2-ol is 3.33 % which also means that the enantiomeric excess(e.e) is 3.33 % excess (+) enantiomer over (-) enantiomer.