Problems Set (Meeting 8)

Announcements (Please read since you will be held to them!)

1. Return of glassware and equipment

a. The lab support usually closes at 5 pm sharp every day. If you do not return the glassware by 5 pm, 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. Note that it is not the instructor's job to provide lab support!

b. Please make sure that you return the equipment that you check out from the instructor i.e., UV-Vis cuvette, polarimetry cells, etc. 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.

2. Instrumentation rooms (YH 6076 and YH 6104)

a. The ATR setup has to be 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. The acetone will leak into the instrument and ruin any further measurements until it has been "aired out", which takes usually overnight! :-(

b. The area around the FTIR spectrometer and the UV-Vis spectrometer has to cleaned after usage. This applies to all students and not just the last student. It is unacceptable that samples, Kim wipes, dirty cleaing wipes, boiling stickes, solutions, etc. are left behind. The same goes for the melting point apparatus. The used melting point capillaries have to be disposed off in the glass trash and not left behind or thrown on the floor. The instrumentation room has gotten increasingly filthy over the past two weeks, which is not acceptable due to safety concerns.

3. 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 rotary evaporator is not permitted here because practicing a simple distillation is part of the teaching goal here.

c. The students are required to review the MSDS for all compounds that they are using in the lab. If CAL OSHA inspects the Chem 30CL labs, they might ask the students about this as well. It will make a very bad impression on you as the student, and will speak poorly for the education at UCLA if you do not know even basic information. The UC has a MSDS database.

4. Quiz 4

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. Provide a balanced chemical equation for the reaction. Identify the reducing and oxidizing reagent in this reaction.

b. Why is it important to use concentrated hydrochloric acid in the reaction?

c. The solid obtained in the first part of the reaction is suspended in water before concentrated potassium hydroxide solution is added. What is the purpose of this step?

d. After extracting the aqueous layer in c., the student proceeds to dry his organic layer with anhydrous sodium sulfate. What do you think about this choice?

e. Why is it important to use a vacuum adapter in the distillation setup? Where is it placed?

f. The student observes two peaks in his GC spectrum. The first peak displays the molecular ion peak at m/z=121 while the second peak has this peak at m/z=155. Identify the compounds arnd explain briefly.

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. Assuming the student isolates 1.50 mL of 2,6-dimethylaniline in step 1. How many milliliters of the acyl chloride should he use in the reaction?

b. Why is it important that the bottle with the acyl chloride remains closed if not in use?

c. What is used as the solvent in the reaction? Rationalize the choice.

d. What are the most important changes in the infrared spectrum going from 2,6-dimethylaniline to a-chloro-2,6-dimethylacetanilide?

e. Why is it important to complete this reaction during the first meeting?