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 Tuesday, January 22, 2008 at 12 pm 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. Borneol is a bicyclic organic compound and a terpene.It can be found in several species of Artemisia and Dipterocarpaceae.The naturally occurring form is d-(+)-borneol. Borneol is used in traditional Chinese medicine as Moxa. An early description is found in the Bencao Gangmu. Borneol is also a component of many essential oils. A student isolates borneol from a natural source. He prepares a solution of 0.25 g of the white solid in 5 mL of ethanol. He places 3 mL of the solution in a polarimetry cell (10 cm) and observes an optical rotation of a= +1.73o. 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. How does the experimenter know that the reaction is proceeding according to plan?
c. Why is water added before the reaction mixture is allowed to cool down?
d. Which advantage(s) does the use of a rotary evaporator have compared to a regular solvent removal?
e. Which solvent is used to acquire the UV-Vis spectrum for the ligand? Which concentration is appropriate here?
f. The phenolic proton shows up at d=13.6 ppm. Rationalize this observation.