Problems Set - Meeting #6

I. Final exam preparation

Since there were several inquiries about how to study for the final exam, here are a few pointers (from the instructor's point of view):

1. Make sure that you understand the procedures and techniques carried out in the lab very well. During the final exam, you need to be able to answer detailed questions to them. This does not mean that you have to memorize the exact amounts of chemicals added, but why certain steps are performed and how they are performed correctly (see lectures, Chem 30BL reader and Survival Kit reader). If these issues are not clear to you, make sure to ask questions (TA, instructor, discussion board, etc.) as soon as possible and not the day before the exam because this usually causes a lot of more confusion than it helps.

2. The exams in the exam reader (the light red thing that you paid for when you bought in the package and have most likely not looked at up to this point) should give you a good idea about the topics that you are expected to master by the end of this course. Use the old exams as self-diagnostic tool and practice. However, memorizing the answers to the questions does not guarantee a high grade in the final because there are always changes in the questions, which most students tend to miss entirely if they are just memorizing the answers. The exam collection contains five exams, which should be more than sufficient to practice in terms of style and timing. It is highly advisable to take the exams in three hours to get accustomed to the timing as well.

3. One of the most important points is to write your own pre-labs and post-labs, and not just copy it from a friend/roommate/etc. and just include your own numbers at best. You are not learning anything this way and most likely will fail the exam miserably, which results in you automatically failing the course because it will be irrelevant on how you performed in the in-lab portion (Note: The instructor is well aware that there is a lot of cheating going on when it comes to prelabs, postlabs, in-lab and online quizzes). As a result, you will have to repeat the entire course again including the in-lab part.

4. Materials covered in lecture like alternative synthetic methods, protective group chemistry, green chemistry, etc. are fair play as well for the final exam. These reactions are not carried out in this course due to safety concerns, cost reasons and/or time constraints. However, these alternatives are important to know because some of the reaction that are carried out in one way in this course would be performed entirely differently in a research lab. Even questions to the extra credit project are ok because the materials are in the course reader or provided as handout as well.

5. No tables will be provided for infrared and NMR analysis because most problems can easily be solved without them. If the student practice reading/analyzing these spectra, this part should not be a problem in the final exam. This requires in infrared spectroscopy the memorization of about ten numbers. In NMR spectroscopy, the effect of hybridization and electronegativity on the chemical shift has to be understood as well as basic splitting patterns in the H-NMR spectrum (i.e., quartet and triplet are indicative of an ethyl group).

6. Finally, make sure that you put enough time aside to study for the final exam. Many students that failed the final exam in past quarters just did not spent enough time to review the material and tried to "wing" the exam. This might work in a humanities course (according to many student comments in the past), but it does not work in a fact-oriented science course, where understanding the concepts is the very first step only, and the ability to apply this newly acquired knowledge the next step. In other words, you can read the readers five times and still fail the final exam with flying colors if you do not understand the concepts. The weekly online quizzes are there to provide you with an immediate feedback on the mastery of a certain technique/topic. If you score below 5 points on a regular basis, you should see your teaching assistant or the instructor to clarify the topic because you most likely missing some important points.

7. The instructor will not sign any late drops forms (dark red form) after meeting 6. Unexcused absence in the lab and/or the final exam or lack of turning in all assignments/reports by the day the final exam is administered will result in an automatic "F"-grade for the course. Late assignments will not be accepted either.

8. The instructor will NOT offer any extra credit assignments after the final exam to boost the grade for students that are not happy with their grades. Please keep this in mind as well since this is a frequent point of discussion when it comes to the final grade assignment. This opportunity has to be offered to all students equally, and frankly speaking, the instructor does not have the time to potentially grade a large number of meaningful assignments that would make a reasonable impact on the student's grade in short period of time (1-2 days). By the time the grades will be assigned for the course, usually the preparations for the next quarter are in full swing already. Aside of that, there are already several opportunities to get extra credit points (Extra credit project, NMR assignment week 10).

9. The term 'final grade' implies that the grades are FINAL. Unless there was a clerical error i.e., adding up points incorrectly, there is NO chance to get a grade change. Arguing about points that you feel that you deserved in the lab and/or the final exam based on your own opinion will not change this either. Please keep in mind that UCLA is one of the top public universities and not a bazaar or market, where you can negotiate the prize. Many students tend to forget this when they complain about their grade. Usually, the instructor refused to write recommendation letters for these students on the account that they do not seem to trust his judgement anyway. Note that the instructor does not write letters for students that only took Chem 30BL because he cannot address a lot of the important points after 10 weeks (i.e., written and oral communication skills).

Bottom line: 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 a lot of the material covered in this course will show up there as well, in one way or the other.

II. Safety (Read carefully)

a. Isopentyl nitrite (=isoamyl nitrite) is a powerful heart stimulant. Breathing it and spillage has to be avoided.

b. 1,2,-dimethoxyethane and isopropanol are flammable. Spillage on the hotplate has to be avoided.

c. For safety reasons, the student should wear clothing made from natural fibers (cotton, wool) to prevent unnecessary damage to him/herself during a fire.

d. The lab coat has to be completely buttoned up and not just with one button as observed with many students in the past weeks.

1. After reviewing the UV-Vis chapter in the reader and the lecture slides, take the online quiz

(http://bacher.chem.ucla.edu/TakeQuiz/?id=c20ad4d76fe97759aa27a0c99bff6710). The quiz is worth 10 points, and has to be taken until one hour prior to the in-lab meeting 6. (Hint: In some cases more than one answer is correct!) Even though you can take the quiz until one hour prior to meeting 6 of your section, you should not delay taking it since there might be some problems with the server. There seem to be problems with some MAC systems as well. After you submit the answers, your score should appear on your screen. If this does not happen, you will have to retake the quiz. (There will not be any possibility to retake the quiz weeks later!). In order to take the quiz, you have to go through a UCLA ICP address. This means that you either have to use your Bruin-Online account or go through the VPN (Vitual Private Network, software can be found here: http://www.bol.ucla.edu/services/vpn/) to have this UCLA ICP address. To log in, use your last name and your student ID. If you are experiencing problems, contact the instructor via email and include your full name (indicated which one is your last name), your student ID and section If the video does not start automatically, you will have to download it first and then start it directly from Real Player or a similar program, etc.


And now to the prelab questions.....

2. Referring to the reaction carried out in the lab, answer the following questions. Provide a balanced chemical equation where appropriate.

a. How is the dienophile obtained in this reaction?

b. Which precautions have to be taken when handling isopentyl nitrite?

c. What is used as solvent in the reaction? Rationalize this choice.

d. Which observations should the student make during the experiment? What should the student do if these observations are not made?

e. After the reaction is completed, a student pours the reaction mixture into a mixture of methanol and water. Which purpose does this step serve?

f. Why is it advisable to use a clean filter flask for the first filtration?

g. Which problems will the student face make during the recrystallization?

h. The final compound displays a double melting point. How is this melting point observed?

i. The student plans to acquire a UV-Vis spectrum for TPN. Which concentration should the solution have?