Problems Set - Meeting #3
Announcements (Please carefully because you will held fully responsible):
1. Safety and other in-lab issues
a. The student has to come properly dressed to the lab. Long pants and closed-toed shoes are mandatory. A lab coat of proper size has to be worn all at times in the lab. The lab coat has to be closed as well. In addition, goggles have to be carired at all times. Failure to follow these rules will lead to a dismissal from the course.
b. All experiments have to be carried out in the hood. This also applies to vacuum filtrations, etc. In addition, the experiments are to be carried out in the scale given in the reader.
c. Upscaling is strictly prohibited. Anybody doing so will be reported to the Dean of Students for cheating. There are reasons why the experiments are carried out in the scale given in your course reader (safety, econonic, etc).
2. Formal report
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. The draft for the report will be due on April 23, 2010 at 4:30 pm.
3. Quiz 1
The first quiz will be administered on Tuesday, April 6, 2009 at 12:00 pm covering the resolution, polarimetry, the introduction to asymmetric synthesis and safety. 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!!!
4. Experimental changes
a. Ethyl acetate will be used instead of dichloromethane during the work-up of the ligand.
b. Acetonitrile should be used to obtain the optical rotation and UV-Vis spectrum.
5. The question below are due with your prelab on 4/6/2010 or 4/7/2010.
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.
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 chemical equation. Why is water used as solvent here?
b. Upon addition of the aldehyde to the solution obtained in a., which observation should the student make?
c. Before allowing the reaction mixture to cool to room temperature, water is added. Why?
d. The crude product is redissolved in ethyl acetate and then extracted with saturated sodium chloride solution. Why?
e. The IR spectrum of the ligand seems to be missing the characteristic broad OH stretching mode of phenols. 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?
g. The student acquires the optical rotation for the ligand. Which solvent and which concentration should be used for this measurement?
h. A student observes a specific optical rotation for his ligand of [a]= -305.0o. Determine the optical purity of the ligand. Comment on the result.