last updated Tuesday, February 12, 2008

Problem set  Meeting 12 

Announcement

1. The instructor will offer an in-lab demonstration of the Grignard setup on February 13, 2008 at 4:00 pm and 4:30 pm in YH 6086. You will get 5 points to attend this meeting.

2. The final version of the paper is due on February 15, 2008 at 5 pm in YH 3077E in printed version (submission via email will not be accepted). Late reports will get 10% of per day late. Make sure that you turn it in online by February 18, 2008 at 11 pm.

3. The next quiz (=quiz 5) will be administered on February 19, 2008 at 12 pm. It will cover the Grignard reaction and the esterification. Make sure that you show up on time. Otherwise you will not be allowed to take the quiz.

...and now to the homework questions

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

a. Why is it important to exclude water as much as possible during the formation of the Grignard reagent? How is this accomplished?

b. How is the Mg metal activated for the reaction?

c. How does the experimenter know that the reaction initiated?

d. At which rate should the etheral bromobenzene be added?

e. After the formation of the Grignard reagent is completed, first the solution is added to dry ice, and then chipped ice is added. Which purpose does each step serve?

f. Why is sulfuric acid added before the mixture is extracted with diethyl ether?

g. How does the final product look like?

2. Theoretical issues

a. Why are alkyl bromides most often used to form Grignard reagents?

b. Grignard reagents are strong bases. Which problems does this pose when it comes to the choice of solvents?

c. Strictly speaking it is wrong to use "RMgBr" to identify a Grignard reagent. Why?

d. What is "Rieke magnesium"?