General Announcement (Please read since you will be held responsible for the content!)

1. Questions in the course

a. It has come to the instructor's attention that some students are not clear about certain policies in this course. There is no such policy in this lab course that 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 (by 5 pm) and safe fashion. The majority of the questions regarding the experiment (theory and practical issues) can be answered by attending the lecture, by consulting the readers or the course website or during office hours (it could not hurt to be coming prepared to them as well because there are often a lot of students that seek answers to various problems). There are a total of ten for this class (six offered by the instructor (admittingly usually very busy because these office hours accommodate three course with a total of 150 students) and four office hours offered by the teaching assistants). A question also should demonstrate the student's ability to analyze the problem and be as specific as possible in his/her inquiry. A comment like "I don't understand this" is not particularly helpful for the person that you are asking for help because they do not know which part of the topic you are having problems with. Also, please also understand that your TA and your instructor have to other responsibilities i.e., conduct research, administrative responsibilities, attend meetings, grading, etc., which means that they are not available 24/7 contrary to many students' believes (i.e., some students send an email in the middle of the night and seriously expect an answer before 8 am the next morning). It is also expected to utilize the existing resources before asking questions. Many students tend to ask questions that can easily be answered by consulting the lecture notes or/and the course readers, which demonstrates poor utilization of the resources provided.

b. If you ask questions of general nature, please do so on the course discussion board so that everybody in the course benefits from the discussion. It is rather pointless for students and the instructor to ask/answer the same questions several times.

c. A frequent complaint in the course is that the isolated yields in the experiments are low i.e., 20-30 %. When comparing the student's yield with the literature yields, which are usually well in excess of 80 %, it should be obvious that the source for the low yield is the student and not the chemistry performed in the lab. The main reason for such low yields is that many students making critical mistakes in the procedure. Some of them are:

• Using too much solvent to dissolve a sample during recrystallization because of improper/no heating or impatience
• Overzealous rinsing of crystals i.e., too much solvent, wrong solvent, or the solvent was not chilled properly, which increases the solubility of the target compound significantly
• Incorrect reaction conditions i.e., reaction not refluxed correctly, which reduces the solubility of reactants and the rate of the reaction significantly, reaction is 'stuck' on an intermediate that displays different physical characteristics
• Poor product recovery from round bottom flask after removal of the solvent
• Leaks in the distillation setup i.e., joints do not fit well together, lack of usage of O-rings in the setup, improper placement of the O-ring
• Being clumsy i.e., spilling sample, not checking the separatory funnel before using it, etc.
• Inappropriate size of the equipment i.e., a small amount of precipitate is isolated using a Büchner funnel instead of a Hirsch funnel, etc.
• Being generally unprepared for the lab (Hint: a Mona Lisa prelab does not mean that you are prepared) or plain not being focused on the task at hand (i.e., chatting about the latest sport results, rumors in the dorms, etc.)

2. Return of glassware

One issue that has to be address here is the return of glassware which has to be clean (independant how how you received it). The lab support usually closes at 5:00 pm sharp every day.

3. Experimental

a. The filtrate from the recrystallization of TPCP has to be collected in a separately marked container (not in the regular waste container!). Thus, it is imperative that the filter flask is clean for this filtration!

b. The TLC samples should be dissolved in ethyl acetate (~5 mg/mL). The teaching assistant will prepare the standards for benzil and dibenzyl ketone.

c. The samples have to be spotted with a capillary pulled from a Pasteur pipette as shown in the video clip.

d. When acquiring FTIR spectra for solids, it is important that the student applies the proper pressure to the sample in order to obtain an useful spectrum. If the sample is only placed loosely on the top of the ATR crystal, the spectrum will exhibit a low signal to noise ratio and many artifacts i.e., negative peaks or extraneous signals at n= ~1740 cm^-1, etc. It is also very important that the crystal is allowed to dry before acquiring any spectra.

e. Finally, it would be very nice if the students would take better care of the glassware. Students that break glassware due to clumsiness or carelessness will receive a significant reduction in points. In some cases, they will also have to pay for the damage because the lab fee does not cover the cost of the item (i..e, separatory funnel, etc.).

4. Safety

a. The glasswaste has to properly disposed of in the blue-white boxes and not in the regular trash! We had problems with waste management in the past quarters, which led to the refusal of the janitors to empty the trash bins because they are afraid that they get injured.

b. Do not pour any organic solvents down the sink. This rule also applies to a solvent like acetone.

c. Students with long hair have to make sure to tie their hair back. The same goes for lose jewelry. The deadly accident about a year back in the chemistry department at Yale University should serve as a reminder to this (http://www.yaledailynews.com/news/2011/apr/13/student-dies-accident-sterling-chemistry-laborator/).

5. Workshop

The third workshop will take place on January 26, 2015 at 5 pm in YH 1044. It will cover the first part of NMR spectroscopy (¹H and ¹³C-NMR). The link for the slides is on the front page.

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. Watch the two videos (Flash) below and then take the online quiz for recrystallization below one hour prior to the 5th meeting.

Recrystallization theory

Recrystallization Practical Aspects

These videos are best viewed with Real Player.

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. If the video does not start automatically, you will have to download it first to your computer and then start it directly from Real Player or a similar program, etc.

http://bacher.chem.ucla.edu/TakeQuiz/?id=aab3238922bcc25a6f606eb525ffdc56

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 5 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, Safari and Google Chrome Browser. The best is using IE 8.0 or Firefox. 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 Aldol reaction carried out in the lab, answer the following questions in a concise fashion. Show pertinent balanced chemical equations where appropriate.

a. Why does the lecture emphasize to use absolute ethanol for the reaction?

b. What is the function of ethanolic potassium hydroxide in this reaction? Show the key intermediate involving this compound.

c. Why is it important that the reaction mixture is refluxed? What does this mean exactly in terms of the setup?

d. Which observations should the student make during the reaction if the reaction was proceeding properly?

e. Which solvent is used to recrystallize the crude product? Rationalize this choice.

f. What is the appropriate the concentration for the solution for the UV-Vis analysis?

g. The students perform TLC in the lab. Assuming they used heptane, acetone and methanol as mobile phases, what would they observe on each plate? Sketch the three plates and explain.

h. What does rule 50 state? Why is it important to follow this rule?