Question

What is the percentage of the R enantiomer in a sample of carvone that has a specific rotation of 30, given that the specific rotation of (R)-carvone is -61?

1) 49
2) 26
3) 51
4) 75

Answer 1

To find the percentage of R-enantiomer, divide the observed specific rotation by the specific rotation of pure R-enantiomer and multiply by 100. The calculation yields approximately 49% of the R-enantiomer in the sample.

Step-by-step explanation:

The given problem is about determining the enantiomeric excess or the percentage of the R enantiomer in a sample of carvone using the observed specific rotation and comparing it with the specific rotation of pure R-carvone. To calculate the percentage of the R enantiomer in the mixture, we use the formula:

Percentage of R enantiomer = (observed specific rotation / specific rotation of pure R enantiomer) * 100%

Substituting the provided values into the formula:

Percentage of R enantiomer = (30 / -61) * 100%

The result is approximately -49.18%. However, since enantiomeric excess cannot be negative, we take the absolute value, resulting in 49.18%. The correct answer from the options given would be 49%.