Problems Set (Meeting 9)
Announcements
1. The next quiz (= quiz 4) will be administered on May 1, 2008 at 12 pm and will cover most likely step 1 and step 2of the Lidocaine project.
2. The final paper will be due on Friday May 9, 2008 at 5 pm in YH 3077E. Late papers will receive 10% off per day late.
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!
5. The crystal on the ATR setup has already been damaged, which should not happen if the setup is used properly. It looks like somebody tried to scrap of the sample with a metal spatula, which is an absolute NO-NO!
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. The procedure emphasizes to use concentrated hydrochloric acid in the first part of the reaction. Explain.
b. Why is it necessary to dissolve the nitro compound in glacial acetic acid before reacting it with SnCl2?
c. The initial reaction affords a white solid. What is this solid and why is it unwise to wash the solid with water after filtration?
d. In the second part of the reaction a solution of the salt from c. is reacted with potassium hydroxide. Which purpose does this serve?
e. The ethereal solution is dried using potassium carbonate. Rationalize this choice.
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. Why is glacial acetic acid is used as solvent in this reaction?
b. Why does the amide precipitate upon the addition of sodium acetate solution?
c. The product has to be dried very rigorously. Explain why.
d. What is the melting point of the product?