General Announcement (Please read!)
1. It has come to my attention that some students are not clear about certain policies in this course. There is no such policy in this lab course which discourages students from asking questions. The reason why you are here is to learn. This should also result in questions from the the student's side, which are welcome by the teaching assistants and the instructor. However, it is expected that the student comes prepared to the lab section in order to be able to complete the experiment in a timely fashion. The majority of the questions regarding the experiment (theory and practical issues) can be answered during lecture, during office hours (there are a total of 13 for this class). A question also should demonstrate the student's ability to analyze the problem and be as specific as possible in his/her inquiry. A simple comment like "I don't understand this" is not particularly helpful for the person that you are asking since they do not know which part of the topic you are having problems with.
2. The filtrate from the recrystallization of TPCP should be collected in a separately marked container (not in the regular waste container!). This also means that it is imperative that the filter flask is clean for this filtration!
3. The IR assignment for this quarter is due by Friday, August 21, 2009 at 5 pm in YH 3077E. No late assignments will be accepted. If you are not at school on Friday, you are welcome to drop off the assignment earlier.
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.
1. Referring to the Aldol reaction carried out in the lab, answer the following questions. Show pertinent balanced chemical equations where appropriate.
a. Why is it imperative to use absolute ethanol for the reaction?
b. The procedure asks to bring the solution to a gentle reflux prior to the addition of the catalyst. Why is this important?
c. Ethanolic potassium hydroxide solution is added as catalyst. What exactly does this catalyst do?
d. Why is it important to place the spin vane properly in the conical vial this time? What does this mean?
e. Which observation will the student make if the reaction is proceeding according to plan?
f. A student obtained 240 mg (dry weight) of the crude product. How much solvent should be used to recrystallize the crude product?
g. A student boils his solution for a long time during the recrystallization. What would he observe?
h. What is the proper concentration for the UV-Vis spectrum here (Hint: the range from 280-600 nm will be measured here)?
i. Why is it important that the entire sample is dissolved when preparing the stock solution?
2. Take the online quiz for recrystallization below one hour prior to the 5th meeting.
http://bacher.chem.ucla.edu/TakeQuiz/?id=aab3238922bcc25a6f606eb525ffdc56
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 . (Hint: In some cases more than one answer is correct!) Even though you can take the quiz until one hour prior to meeting 2 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. 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!). The quiz is worth 10 points.