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.

Announcements

1. The first quiz will be administered on Tuesday, April 8, 2008 at 12 pm covering step 2, step 3 and the theoretical aspects of asymmetric synthesis. Bring a ruler, non-graphing calculator and pen with you. Please make sure that you arrive on time. Late arrivals will not be allowed into the class room since they disturb the rest of the class!! This also means that you will not be allowed to take the quiz!!!

Questions

1. Referring to the oxidation of the benzylic alcohol (step 3), answer the following questions:

a. Why should the reaction be carried out under the hood?

b. The reaction is monitored using TLC. Which samples should be spotted here?

c. The aldehyde exhibits a higher R_f-value than the alcohol and the phenol (=starting material from step 2). Rationalize this observation.

d. After the reaction is completed, the mixture is poured into water. Rationalize this step.

e. A student extracts the mixture from c. with hexane. He observes the formation of white needles. Explain briefly. How should he proceed?

f. Why is methanol used to recrystallize the crude product? Which precaution(s) should be taken here?

2. Referring to the resolution of 1,2-diaminocyclohexane (step 1), answer the following questions.

a. In the beginning of the reaction a small amount of precipitate is observed that dissolves on further addition of the amine, and reappears upon addition of glacial acetic acid. Explain.

b. What is the maximum yield (in g) based on the amounts and chemicals given in the reader? Show all calculations.

c. The accepted optical rotation value for the product of step 1 is [a]_D²⁵= +12.5^o. A student observes a specific optical rotation for his sample of [a]= +11.2^o. Determine the optical purity of the sample. Which impact does this result haves for the project overall?

d. What is the basis of the resolution of the different enantiomers/diastereomers?