(-)-Mandelic acid has a specific rotation of -158°.What would be the specific rotation of a solution which contains 40% (-)-mandelic acid and 60% (+)-mandelic acid?
A)+95°
B)+63°
C)+32°
D)-32°
E)-63°

Question

Quizplus · Accepted Answer

The specific rotation of the solution is calculated by taking the weighted average of the specific rotations of the two enantiomers. The specific rotation of the solution is: (0.4 * -158°) + (0.6 * 158°) = -63.2° + 94.8° = +31.6°, which rounds to +32°.

(-)-Mandelic Acid Has a Specific Rotation of -158°