Problems Set - Meeting #6

General:

Since there were several inquiries about how to study for the final exam, here are a few pointers:

1. Make sure that you understand the procedures carried out in the lab well. This does not mean that you have to memorize the exact amounts added at some point, but why certain steps are performed and how they are performed correctly (see lecture, workshop and Survival Kit reader). If things are not clear to you, make sure to ask questions (TA, instructor, etc.) asap and not the day before the exam.

2. The exams in the exam reader (the pink thing that you paid for when you bought in the package and have not looked at up to this point) give you a good idea about the subjects that you are expected to master by the end of this course. However, memorizing the answers to the questions does not guarantee a higher grade in the final since there are always changes in the questions.

3. One of the most important things is to write your own prelab and postlabs, and not just copy it from a friend/roommate/etc and include your own numbers. You are not learning anything this way and most likely fail the exam miserably, which also means that you are automatically going to fail the course.

4. Finally, make sure that you take enough time aside to study for the final exam. A lot of the students that failed the exam last quarter just did not spent enough time to review the material and tried to "wing" the exam, not very successfully as mentioned earlier in the quarter already.

Bottomline: If you do your own work and understand reasonably well what you are doing in the lab, you should not have any problems to get a passing (and decent) grade in the course. Please keep in mind that many of you are going on to take the MCAT, DAT, PSAT, GRE, etc. and some of the material covered in this course will show up there as well.

And now to something entirely different.....the homework questions:

1. Theory of Diels-Alder Reactions

a. What type of compounds are needed to carry out a Diels-Alder reaction? Provide two examples for each component other than the compounds used in the experiment.

b. One of the features that makes the Diels-Alder useful is its regioselectivity. Explain briefly.

c. Benzyne is considered aromatic despite having 8p-electrons. Explain briefly why.

d. In order for the reaction to occur the diene has to be in s-cis conformation. Explain briefly why.

2. Referring to the reaction carried out in the lab, answer the following questions.

a. How is benzyne obtained in the reaction? Show a balanced chemical equation.

b. The procedure suggests to carry out the reaction in 10 mL round bottom flask. Rationalize this choice.

c. Why is 1,2-dimethoxyethane used in the reaction?

d. Which observations will the experimenter make during the reaction?

e. Which problems is the experimenter facing during the recrystallization step?

3. A UV-Vis spectrum is also obtained for the compound obtained in this week's experiment.

a. Why does the procedure ask to use a quartz cuvette instead of a plastic cuvette this time?

b. Which concentration is needed for the UV-Vis characterization of the TPN? How do you prepare this solution?

c. Why is it important to dissolve the entire sample before diluting the stock solution?

d. Which information should be reported in the postlab write-up from the UV-Vis spectrum?