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, April 14, 2009 at 12:00 pm covering the resolution and the ligand synthesis and techniques involed in these projects. Bring a ruler, non-graphing calculator and pen with you. Please make sure that you arrive on time (this means that you are seated by 11:55 am!!!). Late arrivals will not be allowed into the class room since they disturb the rest of the class!! This also means that 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. Asparagine was the first amino acid isolated in 1806. It is a non essential amino acid because it can be synthesized in the human body from oxaloacetate. A student isolates the compound from asparagus juice in the lab and wants to evaluate its purity.
a. He obtains the optical rotation for a solution of 0.25 g in 5 mL of 5 M HCl. The student observes an optical rotation of a= +1.70o in a 10 cm cell. Determine the optical purity of the sample.
b. What would change if the solution was prepared in water or 0.5 M NaOH solution?
2. Referring to the synthesis and characterization of the Jacobsen ligand, answer the following questions.
a. The initial stage of the reaction the tartrate salt is reacted with potassium carbonate in water. Provide a balanced equation and rationalize the choice of solvent.
b.After the initial part of the reaction, 95% ethanol is added. Explain why.
c.Why is water added to the reaction mixture prior allowing it to cool to room temperature?
d. A student obtains a light brown ligand after evaporation of the dichloromethane. How should he proceed?
e. The IR spectrum of the ligand is missing the characteristic broad OH stretching mode of phenols around 3400 cm-1. Rationalize this observation.
f. Which solvent is used to acquire the UV-Vis spectrum of the ligand? Which type of cuvette should be used here? Where is the UV-Vis spectrometer located that is used in this lab course?