Chemistry Workshops
1. Show how to efficiently carry out the following synthetic transformations, specifying reagents and reaction conditions. Each transformation requires at least two steps.
Tactics for conquering synthetic problems:
a. What could be the penultimate (next to last) compound in the synthetic sequence?
b. How could you convert the penultimate compound to the ultimate compound?
c. If you cannot answer (b), then recycle to (a) and try another penultimate compound.
d. When you get a good final step, then figure out how to make the penultimate compound, following the same logic until you work back to the starting material.
2. See how many synthetic connections you can make on
the chart below. Start with acetylene (ethyne) and any other compounds
containing three carbons or less, and show how to synthesize the
following compounds. Specify necessary reagents, conditions, and
catalysts. In general, more than one synthetic step will be required.
Show multiple steps by linking up compounds on the chart. It will
help to think "forward and backward." For more fun and
challenge, work your way around the perimeter.
3. Alkynes can be made by the dehydrohalogenation of vinylic halides in a reaction that is essentially an E2 process. In studying the stereochemistry of this elimination, it was found that (Z)-2-chloro-2-butene-1,4-dioic acid reacts 50 times as fast as the corresponding E isomer. What conclusion can you draw about the stereochemistry of eliminations in vinylic halides? How does this result compare with eliminations of alkyl halides?
4. Give a detailed mechanism for the reduction of 2-butyne to (E)-2-butene using lithium metal in ethylamine as solvent.. Explain clearly why the product has (E) stereochemistry.
Materials adapted from:
Peer-Led Team Learning: Organic Chemistry, 1/e
Jack A. Kampmeier, University of Rochester
Pratibha Varma-Nelson, St. Xavier University
Donald Wedegaertner, University of the Pacific
Prentice-Hall, 2001, ISBN 0-13-028413-0
http://www.sci.ccny.cuny.edu/~chemwksp/OrganicChem.html
