We made it to the final chapter: Chapter 26 (“Polymers”). Each student is filled with a sense of pride that they have read every chapter in their textbook. Chapter 26 allows us to review mechanisms from throughout the text with real world applications. These applications are good preparation for next week’s final. In discussing them, I tell my students, “It is time to drink some coffee, put socks on, and wear some stylish pants.”
We have just finished studying radicals in Chapter 25. Lucky us, we get to review it right away by learning radical polymerization. Homolysis of initiator followed radical addition to an alkene gives us polystyrene. I tell my students to imagine drinking coffee out of the insulated cup we just “made.” Only a month ago we were in the midst of addition elimination reactions. I explain how these reactions can be used to make socks to wear to school. Addition elimination of adipoyl chloride and hexamethylene diamine can create the nylon we need to keep our feet cool and comfortable. This mechanism refreshes their memory of the nucleophilic addition to a polar pi bond that was constantly reinforced in Chapters 17-21. More addition elimination reaction review gives us the style we need as we complete Fischer esterification and “make” some polyester slacks.
Karty’s polymer chapter serves as an excellent overview of polymer chemistry, covering an appropriate amount of terminology, a variety of polymerization mechanisms, and a solid introduction to polymer characterization. Because the organic curriculum spans so many topics, the amount of polymer coverage in Chapter 26 is just right and allows me to teach what I need in two lectures at the end of the term.
More importantly, Chapter 26 brings chemistry to life with concrete real world applications, that the students truly appreciate, and allows us to review for the final. Other real world examples in this chapter review past fundamental steps. These include electrophilic addition elimination reactions to make Bakelite, and SN2 reactions to make polyethylene glycol.
After learning mechanisms by fundamental step, finishing with polymers is a great way to end organic chemistry instruction. At the end of the term students review mechanisms and put what they learned into perspective. They leave with a vision of how chemical mechanisms are important to all aspects of life and a greater appreciation of what pushing elections can accomplish.
-James Wollack, St. Catherine University
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