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 and office hours. 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 you are having problems with.

2. The IR assignment is due by Friday, October 26, 2007 at 5 pm in YH3077E (not anywhere else). Late assignment submissions will not be accepted. The assignment has bee online for four weeks now, which gave everybody plenty of time to work on it.

3. 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 the filter flask should be clean for this filtration!

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 equations where appropriate.

a. A student uses 95% ethanol for his reaction. Which impact does this choice have on his result?

b. The procedure asks to dissolve both ketones first before proceeding. How is this accomplished and why is this important?

c. Which observations will the experimenter make during the reaction if everything is going according to plan?

d. A student obtained 0.300 g (dry weight) of the crude product. How much solvent should he use to recrystallize the crude product?

e. A student used boiling stones for the recrystallization. Which problem does this pose?

f. Why is extended boiling to dissolve the sample not advisable during the recrystallization process?

g. How is the TLC sample prepared and applied to the TLC plate?

2. A student isolates 1200 mg g of a crude product Z that shows the following solubilities (in g/mL) in 95% ethanol, ethyl acetate and heptane. The impurity to be removed is polar.

a. Which solvent should the student use for recrystallization? Rationalize your choice.

b. Assuming the recrystallization is carried out correctly, how much of the pure product would be recovered? Show your work.

c. Why is it important to allow the solution to cool down slowly during the recrystallization step?

d. Take the online quiz for recrystallization below 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.