last updated Tuesday, October 22, 2002

Problems Set #5

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

1. A student isolated cholesterol from a natural source. The observed rotation a of a 0.4 g sample of cholesterol in 20 mL of chloroform solution contained in a 10 cm polarimeter tube is -0.78^o. Calculate the specific rotation [a]_D²⁰.

2. A sample of synthetic (-)-menthol has a specific rotation of -40^o. What is the composition of the sample? What is the structure of (-)-Menthol and its IUPAC name? Which class of compounds does it belong to?

3. Suggest a brief method to synthesize the "Salen ligand" introduced in lecture.

4. Why are complexes of phthalocyanine and porphine so stable?

5. How can you account for the yellow color of the Jacobsen ligand even though both starting materials are white?

6. What is the function of the potassium carbonate in the reaction (step 4)?