Meeting 8/9 Problem Set

Announcements:

1. The Grignard project will take about 1.5 lab periods. This means that most of the students will finish up the project during meeting 9. In addition, there will be also an NMR lab during this meeting which is also mandatory.

2. If you receive a three-necked flask instead of a round bottom flask, you do not need to use a Claisen adapter in your setup anymore. If you break the round bottom or three-necked flask, you will receive an automatic zero for the lab because it shows carelessness. In addition, you will have to pay for the damage!

3. The assigned reading "Moulay, S., Chem. Educator 2003, 8, 393" is on reserve online. We do not have a subscription for this journal anymore.

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. Show pertinent chemical equations where appropriate.

a. Water should be excluded from the reaction as much as possible. Why is this very important here? How is this accomplished?

b. Why is the reaction mixture cooled during the initial stage of the reaction?

c. What should the student observe during the addition of the benzoin solution?

d. After the reaction mixture is refluxed, 10% sulfuric acid is added. Which purpose does this step serve and which precautions have to be taken here?

e. The combined organic layers are extracted with sodium bicarbonate solution. What would the student observe if this step was skipped?

f. A student uses ether for the recrystallization step. What would he observe?.

g. Why is it important that the solution is not placed in an ice-bath during the recrystallization step?

h. What are the changes in the IR spectrum going from the benzoin to the diol?