Meeting 8 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

Important Announcements:

1. Final exam: December 1, 2003 from 2-4 pm in Bunche 2209a.

2. Review session: November 30, 2003 from 4-6 pm in Young Hall 2200

3. Meeting 8 (Grignard Reaction Part I): 11/19, 11/20 and 11/25. No labs on 11/26.

4. Meeting 9 (Grignard Reaction Part II, NMR work and Clean-up): 12/1, 12/3 and 12/4. Attendance is mandatory.

1. Why do you use diethyl ether and dichloromethane in this reaction?

2. During the work-up, 10% sulfuric acid is added to the mixture.

a. The lab support only provided conc. sulfuric acid. Can he use it for his work-up? If not, how would he obtain ~10% sulfuric acid from concentrated sulfuric acid?

b. Why is it important to add the acid slowly, especially in the beginning. Show pertinent equations.

3. How many products do you isolate from your reaction this week? Rationalize the relative yields for these products.

4. Referring to the recrystallization of the crude product,

a. the procedure ask you not to place the solution in an ice-bath. Why?

b. a student uses low-boiling petrol ether. What would he observe?

c. what is petroleum ether?

d. Often times the solution turns brown or purple during the recrystallization. Explain briefly.

5. Define the following terms:

a. Rieke Magnesium

b. pyrophoric

c. Cadet's Liquid

6. TLC analysis is performed in this experiment as well. Given the following the student can use methanol, dichloromethane, hexane or any mixture of them, which one should he chose if he uses Silica plates? Explain briefly.