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. The feet have to be completely covered. A flame-resistant lab coat of proper size has to be worn all at times in the lab. The lab coat has to be buttoned up as well. In addition, goggles have to be worn at all times to protect the student's eyes. Repeated 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 filtration, extractions, etc. In addition, the experiments are to be carried out in the scale given in the reader. 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, economic, time scale, etc.).
c. When disposing the syringe needles in the sharps container, the caps have to be removed.
d. If the reaction afforded a very fine precipitate, a Büchner funnel should be used for filtration.
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 by October 18, 2013 at 4:30 pm.
3. Quiz 1
The first quiz will be administered in lecture on October 3, 2013 at 12 pm (covering the introduction to asymmetric synthesis and the resolution step). It is the student's responsibility to arrive on time which means that you have to be seated by 11:55 am!!!! Late arrivals (even if it is only one minute) will not be allowed to take the quiz, which means that you will receive an automatic zero score for the quiz. If you do not place your name on the quiz to assume authorship during the alloted time, you will receive a zero score as well! You cannot add the name after time was called because this is considered cheating. It is also not allowed to start writing (including writing down your name on the quiz) until you are allowed to do so by the instructor. Failure to follow these rules will result in an immediate dismissal from the quiz resulting in a zero score. Spelling errors will cause in an 0.5-point penalty per incident. Carbon and nitrogen atoms with five or more valences receive a 2 point deduction per incident, so do other atoms that exceed the maximum number of valences.
4. Lecture materials
a. In case you did not get the emails that were sent out to the class, the lecture slides are posted here here. Make sure that you look at them before you attend the lecture.
b. The podcast can be found on Bruincast. The waitlisted students should be able to access this information later this week or early next week (depending on when they are being officially enrolled in the course).
c. Students that did not take Chem 30AL and Chem 30BL should review the basic techniques asap. Several videos covering recrystallization, extractions, pulling capillaries for TLC, etc. can be found on the Chem 30BL course website.
5. The question below are due with your prelab on October 3, 2013 or October 4, 2013 depending on when your section meets.
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. During the initial stage of the reaction, the tartrate salt is reacted with potassium carbonate. Provide a balanced chemical equation using the proper structures for the organic compounds.
b. Why is the reaction in a. carried out in water? Why is 95 % ethanol added afterwards?
c. Upon addition of the aldehyde solution to the boiling solution in b., which observations should the student make?
d. Which solvent is used to dissolve the crude product to perform the extractions?
e. Why is the solution obtained in d. treated with a saturated sodium chloride solution?
f. How is the ligand recovered after the organic layer was dried over anhydrous sodium sulfate?
g. The infrared spectrum of the ligand exhibits a peak at n=1630 cm-1. Rationalize this observation.
h. The literature reports signals at d= ~72 ppm and d= ~166 ppm in the 13C{1H}-NMR spectrum of the ligand among many other signals. Rationalize these observations.
i. The student acquires the optical rotation for the ligand. He dissolves 35.0 mg in 7.00 mL of hexane and determines the optical rotation for this sample to be a= -1.45o. Determine the optical purity of the sample considering that the specific optical rotation of the (R,R)-enantiomer of the ligand is [a]= -315o. Show your work. Discuss the result.