Question

For the given ee values, calculate the percentage of each enantiomer present.

a. 90% ee

b. 99% ee

c. 60% ee

Short answer

1. 95% A and 5% B.
2. 99.5% A and 0.5% B.
3. 80% A and 20% B.

Step-by-step solution

Enantiomeric excess (ee) 

The enantiomeric excess comes to explain the particular enantiomer’s excess amount in the given mixture.

Calculation of the ee

The formula to calculate the ee is as follows:

$\text{ee=\%ofoneenantiomer-\%ofotherenantiomer}$

Explanation

a. From the formula of ee, we can easily calculate the percentage of enantiomers as:

90% ee means 90% excess of A, and 10% racemic mixture of A and B (5% each); therefore, 95% A and 5% B.

Therefore, the percentage of enantiomers is 90 % of A and 5% of B.

b. From the formula of ee, we can easily calculate the percentage of enantiomers as:

99% ee means 99% excess of A, and 1% racemic mixture of A and B (0.5% each); therefore, 99.5% A and 0.5% B.

Therefore, the percentage of enantiomers is 99.5 % of A and 0.5% of B.

c.From the formula of ee, we can easily calculate the percentage of enantiomers as:

60% ee means 60% excess of A, and 40% racemic mixture of A and B (20% each); therefore, 80% A and 20% B.

Therefore, the percentage of enantiomers is 80 % of A and 20% of B.