last updated Tuesday, May 05, 2009

Problem set  Meeting 12 

Announcement

1. Make sure that you turn in a hardcopy of your research paper by Friday, May 8, 2009 at 5 pm and the electronic version to turnitin.com as well (CourseID: 2703590, Password: Chem30CL for Spring 2009 (no spaces!)). Late reports will be deducted points (10% per day including the weekend and independent why the report is late). If you do not submit the report online by Monday, May 11, 2009 at 10 pm, you will receive a "zero" score for the paper. In addition, it will be reported to the Dean of Students. 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 try to use your own words as much as possible. 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.

2. There will be an in-lab demonstration on how to set up the Grignard setup on Wednesday, May 6, 2009 at 4 pm in YH6086. Many TAs will provide extra credit for attending this demonstration.

3. The next quiz (=quiz 5) will be administered on Thursday, May 7, 2009 at 12 pm and will cover steps 3 of the Lidocaine project, MS, GC and NMR spectrocopy of epoxides. 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

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

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

b. Why is it necessary to crush the magnesium turnings before placing them in the flask? Which color should the Mg-turnings have?

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. It is also important that the bromobenzene solution is added at the proper rate. Explain briefly.

e. After the formation of the Grignard reagent is completed, first the solution is cooled and then added to dry ice. Which purpose does each step serve and which precaution should be taken here?

f. Afterwards, the mixture is treated with chipped ice and conc. sulfuric acid. Which purpose does this serve?

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

h. Hydrochloric acid is added to the layer containing the target compound. What should the student observe here?