When talking with chemist friends about their organic chemistry experience as students, many of them remember the mechanism questions as the most difficult; the last questions on each exam, the “A-student versus B-student” questions, were always mechanisms to struggle through. When I’ve explained that my school follows a mechanistically driven approach to organic chemistry, the response is sometimes one of surprise. Why are you making a tough subject even more difficult by focusing only on the difficult stuff? Doesn’t this make the course too high a level for most of your students?
I argue that having students learn the “why” and “how” of reactions actually makes it easier for them to succeed. Approaching organic chemistry as first a bunch of reagents and reactions to memorize, with the mechanisms reserved as side-explanations and challenge questions, does the students a great disservice. Most of my students cannot memorize enough to survive, through memorization alone, both semesters of organic chemistry! Even those students who can memorize vast quantities of information and regurgitate appropriately certainly will forget that information in time for the MCATs, GREs, or simply their biochemistry courses. Reagents make no sense if you cannot approach them like a chemist and think about what will happen at a molecular level. With a good understanding of mechanistic theory, all the reagents and their behaviors really do simply fall into place. A mechanistically-organized course allows for understanding instead of memorizing.
I always taught my organic chemistry sequence as a mechanistically-driven course, since it seemed to me that students remembered reagent behavior much better if I started out with why reactions occurred a certain way (mechanisms). Even so, come late-March—the start of carboxylic acid derivatives—it often felt that my class was built as a house of cards, ready to fall at any moment. There were just so many reagents to discuss, and students simply kept getting confused as to which one did what. Reducing agents/oxidizing agents/base catalyzed/acid catalyzed…everything started to blend together, leading to some amazing acts of desperation on exams (that base did what now?).
While I was trying very hard to use mechanisms as the explanation for everything we saw in class, I didn’t start my semester with mechanistic steps and build outwards (as I do now). I believe my approach helped many students, but I still had too many hopelessly lost by late-March/April. However, it wasn’t the mechanism problems that they struggled with, as some of my chemist friends might believe, but the total-synthesis and the just-provide-the-product type problems. I did sometimes worry that, because I focused so much on the ‘why’ (mechanisms) that I had neglected the ‘how’ (reagents).
I believe now that it wasn’t that I spent too little time on the reagents, but not enough time on mechanisms. I’ve since developed my course, including adopting Karty’s text, to focus even more on mechanisms. I begin the year with Chapter 7 (all the mechanistic simple steps) and then tie everything back to this chapter throughout the year. This has made a large positive impact on my course. Reagents and reactions are all firmly grounded in why/how they function, which makes them easier to remember since the students have the ‘hint’ of synthetic usefulness based on their understanding of the mechanisms. Students no longer ask which way something is going to react (is this one of those attach then protonate or protonate then attack reagents?) since they are extremely comfortable looking at the system and figuring it out.
Students remember better if they understand what is going on, which is the whole point behind a mechanistically-organized course. It does not make the course more difficult, it actually makes understanding a great deal easier.
-Michelle Boucher, Utica College
