Answer
The percent e.e. is 33.3%. The ratio of S to R is 2:1, which is same as 66.6:33.3. The e.e. is the difference between the two percentages, 66.6-33.3=33.3=e.e.
Work Step by Step
Specific rotation is equal to rotation of pure enantiomer x e.e. The rotation of pure (+)-butan-2-ol is 13.5 degrees. 13.5x33.3%=4.4955 degrees.