Question

A. What is the percentage enantiomeric excess of a product if the observed specific rotation is +44 degree. but the specific rotation of the pure enantiomer is +56 degree? b. Is the compound predominantly R or S stereoisomer? Discuss why a liquid-liquid extraction usually involves several small steps (say, 3 times 20 ml) rather than one big (say. 1 times 60 ml). Describe the set-up and theoretical principle in a fractional distillation. Include a discussion of the concept of a theoretical plate. Write as much detail as you can.

Answer 1

1)

a) enantiomeric excess = observed rotation x100/ specific rotation of pure isomer

=+ 44 x100/56

= 78.57 %

b) the enantiomeric excess is 78.57% shows that the + isomer is 78.57(because the observed rotation is positive) and 21.43 is (-) isomer.

So the compound has + isomer predominantly.