What is the percentage of the R enantiomer in a sample of carvone that has a specific rotation of −20, given that the specific rotation of (R)-carvone is −61?

Question

Quizplus · Accepted Answer

To find the percentage of the R enantiomer, we can use the following formula: 
% of R enantiomer = (observed specific rotation / specific rotation of pure R enantiomer) x 100

Plugging in the values given: 
% of R enantiomer = (-20 / -61) x 100 = 32.8%

However, this only gives us the percentage of the R enantiomer. To find the percentage of the S enantiomer, we can subtract this value from 100.

% of S enantiomer = 100% - 32.8% = 67.2%

Therefore, the answer is B (66.5% is the closest option to our calculated value of 67.2%, and is likely due to rounding differences).

What Is the Percentage of the R Enantiomer in a Sample