Problems Set - Meeting #4
Announcements:
1. Make sure that you make progress on your formal report as well in terms of literature search and writing the parts that you completed already in the lab.
2. The second quiz will be administered on Monday, October 22, 2007 at 10 am covering the resolution step and the ligand synthesis. Please make sure that you show up on time. If you arrive late, you will not be allowed to take the quiz.
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. Camphor is a waxy, white or transparent solid with a strong, aromatic odor. It is considered a terpenoid and found in wood of the Camphor laurel (Cinnamomum camphora), a large evergreen tree found in Asia (particularly in Borneo and Taiwan, hence its alternate name). It also occurs in some other related trees in the laurel family, notably Ocotea usambarensis. It can also be synthetically produced from oil of turpentine. It is used for its scent, as an ingredient in cooking (mainly in India), as an embalming fluid, in religious ceremonies and for medicinal purposes. A major source of camphor in Asia is Camphor basil. A student isolates camphor from one of these sources. He prepares a solution of 0.5 g of white solid in 10 mL of chloroform. He places 4 mL of this solution in his 10 cm cell and obtains an optical rotation of a= +2.15o. Determine the optical purity for the sample.
2. Referring to the synthesis and characterization of the Jacobsen ligand, answer the following questions.
a. Why are two equivalents of potassium carbonate needed in this reaction? Show pertinent equation(s).
b. Why in the reaction in step a. carried out in water?
c. Why is water added before the reaction mixture is allowed to cool down?
d. Often times, the crude ligand appears as light-brown solid. How can the ligand be purified?
e. Which solvent is used to acquire the UV-Vis spectrum for the ligand? Which concentration is appropriate here?
f. The imine proton shows up at d=8.34 ppm. Rationalize this observation.