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. Water has to be excluded from the reaction as much as possible. Explain. How is this accomplished?

b. The reaction mixtured is placed in an ice-bath in the beginning of the reaction. Explain.

c. During the work-up, a student is asked to add 10% sulfuric acid to the reaction mixture. Show pertinent equations.

d. After the organic layer is dried over magnesium sulfate, the solvent is 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. What would he observe?

f. What has to be considered during the recystallization step?

2. Referring to the GC spectrum that has to be acquired for crude and the final product, answer the following questions.

a. How is the sample for the GC spectrum prepared?

b. Most students will see at least two peaks in the spectrum. How can one determine which compound belongs to the desired product?

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

a. Assume that the following three solvents are given: petroleum ether, acetone and ethanol. 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. The ¹³C-NMR spectrum for the product shows a large peak at ~40 ppm. Explain.