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

1. During the work-up, a student is asked to add 10% sulfuric acid to the reaction mixture.

a. The lab support only provided conc. sulfuric acid for the experiment. Can he use it for his work-up? Explain briefly.

b. Why is it important to chill the acid before adding it slowly?

2. Referring to the recrystallization of the crude product, answer the following questions.

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

b. a student uses pentane as solvent. What would she observe?

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

3. A students is planning a Grignard reaction and checks for solvents available in his lab. He finds dimethoxyethane, ethyl acetate and hexane in the solvent cabinet. Which one should he choose if any? Explain briefly.

4. Why is diethyl ether less polar than tetrahydrofuran? Explain briefly.