Problems Set (Meeting 9)
Announcements
1. The next quiz (= quiz 4) will be administered on April 30, 2009 at 12 pm and will cover step 1 and step 2 of the Lidocaine project. Make sure that you are in the room by 11:55 am!
2. The final paper will be due on Friday May 8, 2009 at 5 pm in YH 3077E as hardcopy. Late papers will receive 10% off per day late including the weekend. The papers have to be submitted online to www.turnitin.com by Monday, May 11, 2009 at 10 pm. The course ID is "2703590" for Spring 2009 and the password is "Chem30CL".
3. You should finish the first two steps of the lidocaine project on the first day of the project.
4. The instrumentation room in the first floor (YH 1102) should be left in proper conditions. Lately, there has been an increasing mess i.e. Kim wipes all over the place, unclaimed solutions and glassware, 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!
Questions:
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 conc. hydrochloric acid used for this reaction?
b. What is the nitro compound dissolved in glacial acetic acid?
c. How many equivalents of SnCl2 are required to perform the reaction? Explain.
d. The initial reaction affords a white solid. A student isolates the salt by filtration and washes it with water. What would he observe?
e. In the second part of the reaction a solution of the salt from d. is reacted with concentrated potassium hydroxide solution. Which purpose does this serve?
f. Student X attempts to dissolve the salt, but seems to have a lot of problems to do so. What is the problem and how should he proceed?
g. What is used to dry the organic layer? Rationalize this choice.
h. Why is a conventional distillation used in this experiment?
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. Rationalize this choice.
b. Why does the amide precipitate upon the addition of sodium acetate solution?
c. Why has the product to be dried very thoroughly before moving on to the next step?
d. What are the characteristic changes in the IR spectrum for the product?
e. What is the melting point for the product?