Question

? What is the enantiomeric excess of an adrenaline sample that has a specific rotation of - 47.7? pure adrenaline has a specific rotation of -53, 4 pts

Answer 1

1)

optical purity = observed specific rotation / specific rotation of pure

                     = - 47.7 / - 53.4

                     = 0.893

enantiomeric excess %ee = optical purity x 100

                                        = 0.893 x 100

enantiomeric excess %ee   = 89.3 %

2)

concentration = 4 / 40 = 0.1 g/ml

length = 20 cm = 2 dm

observed rotation = 14.4°

specific rotation = observed rotation / length x concentration

                          = 14.4° / 2 x 0.1

                          = 72°

specific rotation    = + 72°