Meeting 8/9 Problem Set

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. Referring to the Grignard reaction, answer the following questions.

a. Explain why water should be excluded as much as possible from the reaction. Show pertinent equations. How is this accomplished?

b. Why is the reaction mixtured is placed in an ice-bath in the beginning of the reaction?

c. During the work-up, a student is asked to add 10% sulfuric acid to the reaction mixture. Show pertinent equations. Which precaution have to be taken here?

d. After the organic layer is dried over magnesium sulfate, the solvents are removed. Unfortuantely, not all of it can be removed in a warm water bath. Why is this not possible and how can the remaining solvent be removed?

e. A student uses low-boiling petroleum ether as solvent for the recrystallization. What would he observe?

2. Most students will see at least two peaks in the GC spectrum. How can one determine which peak belongs to the desired product? What is the most likely source of the other peak(s)?

3. Referring to the TLC part of the experiment, answer the following questions.

a. Assume that the following three solvents are given: petroleum ether, dichloromethane and methanol. Which single solvent would be most suitable for the TLC in order to accomplish a good separation between the product and the reactant?

b. How could you improve the separation using these solvents?

c. What is used to apply the sample to the TLC plate?

4.Why do we not observe the formation of a racemic mixture in this experiment?