Problems Set - Meeting #6

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 and are able to answer detailed question 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 lecture 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 because this usually causes a lot of confusion.

2. The exams in the exam reader (the light green 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 subjects that you are expected to master by the end of this course. Use the exams as self-diagnostic and practice tool. However, memorizing the answers to the questions does not guarantee a higher grade in the final since there are always changes in the questions, which most students will miss entirely if they are just memorizing the answers.

3. One of the most important things is to write your own prelabs and postlabs, 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 also means that you are automatically going to fail the course. If you fail the exam, 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 quizzes). As a result, you will have to repeat the entire course again including the in-lab part.

4. Finally, make sure that you put enough time aside to study for the final exam. A lot of the students that failed the 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, but it does not work in a fact- oriented science course, where understanding the ideas and concepts is the very first time only, and application is the second step.

5. The instructor will not sign any late drops forms (dark red form) after week 7. Unexcused absense 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.

6. The instructor will NOT offer any extra credit assignments 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 such a short period of time (1-2 days). By the time the grades will be assigned for the course, the preparations for the next quarter are in full swing already.

7. The term 'final grade' means 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. 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.

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 the prelab questions.....

1. After reviewing the TLC chapter in the reader, take the online quiz

(http://bacher.chem.ucla.edu/TakeQuiz/?id=d3d9446802a44259755d38e6d163e820). 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, section and TA. (Hint: Think very careful about each response since many of the questions have more than one answer to them! Many students come up with the most obvious one and miss some of the details which leads to a zero score for the question!) 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 or the login. Also, there seem to be problems with MAC systems, the Safari and Google Chrome Browser. The best is using IE 7.0 or Firefox. . You can view the quiz as often as you like (even print it out), but only take it once. After you submit the answers, your score has to 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 since you are supposed to show preparedness at the point in time when you enter the lab!). The quiz is worth 10 points.

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

a. How is benzyne obtained in the lab? Which function does the compound have in the reaction?

b. Why is it imperative that TPCP is present in the solution right from the start?

c. Instead of diethyl ether, 1,2-dimethoxyethane used as solvent in the reaction. Rationalize this choice.

d. Why is it not advisable to run the reaction in a conical vial?

e. Which observations should the student make during the reaction if the reaction proceeded as planned?

f. After the reaction is completed, the reaction mixture is poured into a mixture of water and methanol. Rationalize this choice. How is the resulting precipitate isolated? (be specific here!)

g. The crude product is recrystallized from iso-propanol. Which observation will the student make during the recrystallization? Rationalize this observation.

h. The final product exhibits a double melting point. What does this mean? How can this observation be rationalized?