Optical activity of an enantiomeric mixture is + 12 . 6 ° and the specific rotation of + isomer is + 30 ° . The optical purity is____ %

Step-by-step solution

The "optical purity" is a comparison of the optical rotation of a pure sample of unknown stereochemistry versus the optical rotation of a sample of pure enantiomer. It is expressed as a percentage. If the sample only rotates plane-polarized light half as much as expected, the optical purity is 50%. % optical purity = observed   rotation   of   mixture × 100 rotation   of   pure   enantiomer = + 12 . 6 ° + 30 ° × 100 = 42