Problems Set (Meeting 9)
Announcements
1. The next quiz (= quiz 4) will be administered on October 28, 2008 at 11 am and will cover step 1 and step 2 of the Lidocaine project.
2. The final paper will be due on Friday November 7, 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. On Tuesday, October 21, 2008 the class will meet for lecture in YH 4335 and YH 4336 (Chemdraw training).
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. What would happen if the student used 3M HCl instead?
b. Why is glacial acetic acid used as solvent here? What is this anyway?
c. How many equivalents of SnCl2 are required to perform the reaction?
d. The initial reaction affords a white solid, which is isolated by filtration. What is this solid and why should it not be washed with water?
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. How should he proceed?
g. How is the final product isolated after the drying step? Why is this technique used?
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. Why has the product to be dried very thoroughly before moving on to the next step?.
d. What is the melting point of the product?