Week 7 Problem Set 30 BL (Coumarin Synthesis and Photochemical Synthesis of Benzopinacol)

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.

Administrative Issues

1. Please consult your teaching assistant directly in order to find out when a particular post-lab report is due. The yellow reader outlines the tentative schedule, which has to be adjusted from time to time depending on how the section proceeds with the in-lab work.

2. If you have questions of general nature, please post them on the course discussion board instead of sending it to the instructor. Answering the same question several times is not productive for anybody.

1. After watching the following video (MP4-format), reviewing the TLC and the HPLC chapter in the SKR and the reviewing the lecture material, take the online quiz.

Quiz: (http://bacher.chem.ucla.edu/TakeQuiz/?id=d3d9446802a44259755d38e6d163e820). The quiz is worth 10 points, and has to be taken until one hour prior to the in-lab meeting 7. (Hint: In some cases more than one answer is correct!) Even though you can take the quiz until one hour prior to meeting 7 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 .

Prelab questions (due at the beginning of meeting 7):

1. Referring to the Coumarin experiment:

a. What is the function of the Amberlyst A15 in this experiment? Show the key intermediate.

b. Why is it important that the hot reaction mixture is insulated after removing it from the microwave?

c. Which precautions have to be taken when running the reaction in the microwave?

d. The crude is treated with a hot solvent mixture (methanol:water=5:1). What should the student observe at this point?

e. The coumarin displays fluorescence. The student uses a UV-lamp that has two wavelengths available as light source. Which of these two wavelengths is used for the test? Rationalize the choice.

f. How many signals does the product display in the ¹H-NMR spectrum? Where are they in the spectrum and how do they look like?

2. Referring to the Photochemical Synthesis of Benzopinacol:

a. What is used as reaction vessel in this reaction? Where is it obtained?

b. Why is it important to heat the mixture of benzophenone, glacial acetic acid and isopropanol? Which temperature is the student looking for?

c. Why is it important that the vial has a septum on the inside of the cap?

d. The student submits a sample for HPLC analysis. How is the sample prepared?

e. What are the most important changes in the infrared spectrum?