Problems Set - Meeting #4
The second quiz will administered on Tuesday, April 19, 2005 at 11 pm in CS76. 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. Glutamine, one of the twenty amino acids, can be found in protein powders, beans, meats, fish, poultry, dairy products. It is extensively used in the gut and immune system. A sample isolated from one of the previously mentioned source exhibits an optical rotation of a=+0.75o for a 5% solution in 1N HCl in a 5 cm cell. Determine the optical purity of the sample and the absolute stereochemistry of the glutamine.
2. Referring to the synthesis and characterization of the Jacobsen ligand, answer the following questions.
a. Potassium carbonate used in the initial stages of the rection. Explain briefly why.
b. A student was not able to crystallize the crude aldehyde. However, he knows from his TLC that there is very little alcohol left in the sample and he decides to use the obtained oil. What should he do to ensure the completeness of his ligand synthesis?
c. A student runs out of sample and decides to use the solution that he used to acquire his UV-Vis spectrum for his optical rotation measurement. Would this work in this experiment?
d. The C=N stretching mode is located around 1630 cm-1 and usually is less intense than the C=O peak from the starting aldehyde. Rationalize these observations.
e. Where does the hydrogen of the imine function (H-C=N)appear in the 1H-NMR spectrum? How about the carbon atom of the imine function? Rationalize these observations.