ATTN: answers to the below questions are due at the start of your second lab period; these answers should be part of your pre-lab write-up.

1. A student has the task to isolate (S)-(+)-ibuprofen from a racemic mixture of ibuprofen.

a. The student has 10 g of the racemic mixture. Suggest a method to isolate the desired enantiomer.

b. The student obtains 4.2 g of the (S)-(+)-ibuprofen. Calculate the yield.

c. For the isolated enantiomer, he observes an optical rotation of a=2.8^o for a 5% solution in a 10 cm cell. What can he conclude about the purity of his sample?

d. Suggest two other methods to determine the optical purity of his sample?

e. Why is it not possible to separate enantiomers by simple distillation or recrystallization?

2. Why is it important to finish the resolution step during the lab period?

3. Referring to the oxidation reaction (step 3b), answer the following questions.

a. Why does the temperature has to be carefully controlled in this reaction?

b. How can you check if the reaction is completed?

c. How is the aldehyde purified?

d. What is the melting point of the aldehyde (6) and the benzylic alcohol (5)?

e. What are the most important changes in the IR spectrum of the aldehyde?