Problems Set - Meeting #4
The second quiz will administered on Thursday, October 14, 2004 at 12 pm in YH2200. Please make sure that you are on time in order to take full advantage of the time allotted for the quiz.
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.
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. Referring to the synthesis and characterization of the Jacobsen ligand, answer the following questions.
a. How is the diamine obtained from the ammonium salt (3) in this reaction? Provide a balanced chemical equation.
b. Why is water added to the reaction mixture before it is allowed to cooled to room temperature?
c. Which concentration(s) should be used when acquiring the UV-Vis spectrum of the ligand?
d. What is the expected specific optical rotation for the pure (R,R)-form of the ligand?
e. A student observed an optical rotation of a= (-9.25o) for a 3.00 % solution of the ligand in a 10 cm cell. Which conclusions can she draw about the optical purity of her ligand?
f. Why is saturated sodium chloride solution used during the work-up?
g. Why does the IR spectrum of the ligand not show the characteristic broad OH-peak around 3400 +/- 200 cm-1 despite the fact that the product possesses two OH-groups?
h. Where do you expect the C=N-stretching frequency to appear in the IR spectrum? Do you expect this peak to be stronger of weaker than the C=O mode? Explain briefly.
i. Where does the hydrogen of the imine function appear in the NMR spectrum? How about the carbon atom of the imine function? Rationalize these observations.