Problems Set (Meeting 9)

Announcements (Please read!)

1. Return of glassware

The lab support usually closes at 5 pm sharp every day. If you do not return the glassware by then, you will not be able to retrieve your student ID. This can become a huge problem if this is your access key to your university apartment and your dinner. So please make sure to return the glassware clean and on time. Failure to do so will result in a deduction of in-lab points.

2. Return of equipment

Please make sure that you return the equipment that you check out from the instructor immediately after your lab section is done. You cannot take the equipment home under any circumstances!!. Please keep in mind that the equipment is shared with all students in the lab .Failure to observe this rule will result in a significant point penalty.

3. Instrumentation rooms (YH 6086 and YH 6104)

a. The instrumentation rooms in the sixth floor should be left in proper conditions. Lately, there has been an increasing mess i.e. dirty Kim wipes all over the place (which should not be used to clean the ATR setup!), unclaimed solutions and glassware, melting point tubes, etc. In addition, students do not seem to feel that it is necessary to wear goggles in this room, which is not acceptable either. Please keep in mind that you are still handling chemicals!

b. The ATR setup is cleaned the special wipes that are available from lab support. The wipes should be moistened prior use. It is not acceptable that the student "bathes" the ATR setup in acetone.

4. Experimental

a. You have to finish the first two steps of the lidocaine project on the first day of the project. The anilide has to dry for a significant amount of time in order for the the lidocaine synthesis to work properly.

b. The diethyl ether is distilled off using a simple distillation setup as described in the reader. The use of a rotavap is not allowed here since practicing a simple distillation is part of the learning goal here.

5. Quiz 4

The next quiz will be administered on Thursday, April 29, 2010 at 12 pm. It will cover the entire Lidocaine project. It is highly advisable for many students to do some more serious studying since the scores are lacking badly. This also applies to topics like safety and basic techniques.


Questions (due on 4/27 or 4/28):

1. Referring to the conversion of 2,6-dimethylnitrobenzene to 2,6-dimethylaniline (step 1), answer the following questions. Show pertinent chemical equations where appropriate.

a. Why is 2,6-dimethylnitrobenzene dissolved in glacial acetic acid?

b. Why is it important that the reaction mixture is strongly acidic during the first part of the reaction?

c. What is used as the reducing reagent? How many equivalents are required?

d. The initial reaction affords a white solid, which is isolated by vacuum filtration, but subsequently not washed with water. Explain.

e. A student attempts to dissolve his salt in the 30 mL of water and experiences problems. What is the reason and how should he proceed?

f. After solving the problem above, he proceeds to extract the mixture with diethyl ether. How much is appropriate here?

g. Why is a simple distillation used in this experiment?

h. How does the final product look like?

2. Referring to the conversion of 2,6-dimethylaniline to a-chloro-2,6-dimethylacetanilide (step 2), answer the following questions. Show a pertinent chemical equations where appropriate.

a. Glacial acetic acid used as solvent in this reaction as well. Rationalize this choice.

b. Many students will observe pink or purple solutions when they dissolve the 2,6-xylidine. Rationalize this observation.

c. When the student opens the supply bottle for the acetyl chloride, he observes "white smoke". Explain.

d. After the reaction is completed, a solution of sodium acetate is added. Rationalize this step.

e. Why should this step be completed during the first meeting?