last updated Tuesday, February 09, 2010

Problem set  Meeting 12 

Announcement

1. Make sure that you turn in a hardcopy of your research paper by Friday, February 12, 2010 at 4:30 pm and the electronic version to turnitin.com as well (CourseID: 3000041, Password: Chem30CL for Winter 2010 (no spaces!)). Late reports will be deducted points (10% per day including the weekend). If you do not submit the report online by Monday, February 15, 2010 at 10 pm, you will receive a "zero" score for the paper. In addition, it will be reported to the Dean of Students for attempted cheating. Any plagiarism, partial or full resubmission of a papers or/and other forms of cheating will result in a report to the Dean of Students as well. Make sure that you cite your sources and use your own words. Here is a checklist what should be included into the report. If you have any questions, please contact your TA or instructor asap, and not an hour before the submission deadline. The final version has to be submitted in a small binder! Loose paper collections, large binders or folders will not be accepted!!!

2. There will be an in-lab demonstration on how to set up the Grignard setup on Wednesday, February 10, 2010 at 4 pm in YH 6086. Many TAs will provide extra credit for attending this demonstration.

3. The next quiz (=quiz 5) will be administered on Wednesday, February 17, 2009 at 11 am and will cover MS, GC and NMR spectrocopy of epoxides and the Grignard reaction. Make sure that you show up on time. Otherwise you will not be allowed to take the quiz.

...and now back to the chemistry....the homework questions (due 2/11 or 2/12)

1. Referring to the Grignard reaction, answer the following questions. Show chemical equations when appropriate.

a. Like in many other reactions, water poses a huge problem in this reaction. Why? How is the amount of water minimized?

b. Like many metals, magnesium is coated with a layer of its oxide. Which problem does this pose? How is this problem solved in the lab?

c. How does the experimenter know that the reaction initiated? What could he do if the reaction did not to start on its own?

d. Why is it important to add the bromobenzene solution at the proper rate?

e. After the formation of the Grignard reagent is completed, the solution is added to dry ice. Which purpose does this step serve?

f. Afterwards chipped ice and concentrated sulfuric acid are added as well. Which purpose does this step serve?

g. The organic layer is extracted with sodium hydroxide solution. Explain briefly why.

h. The crude product appears as a pale yellow solid. Rationalize this observation.