Research in chemical education has repeatedly trumpeted the message students do not see things the way we see them. However articulate or engaging we are, explanations, demonstrations, and worked examples do not guarantee that students view chemistry the way we do.
For example, when I recently asked students to direct me on how to draw the arrows for an SN2 reaction, I expected them to tell me to first draw an arrow from the nucleophile to the carbon:
And then the arrow that moves the shared pair between the carbon and the leaving group:
However, on multiple occasions this semester, different students directed me to do the reverse. First, they wanted to move electrons to the leaving group:
And then bring in the electrons from the nucleophile:
I still do not understand why they would perceive an SN2 reaction as proceeding in this fashion. They didn’t get it from me—honest!
While this particular example may be as new to you as it was to me, we probably share a list of “things students do that drive me crazy”: strong bases appearing miraculously in acidic solution, protons teleporting from one part of molecule to another, double bonds in benzene circled and labeled “alkene,” etc.
After I started teaching organic chemistry, I catalogued recurring issues and included “preemptive strikes” in a list I would give students entitled “Organic Chemistry Leitmotifs.” Several were humorous attempts at saying, “Don’t do that!”
I am happy to report that students no longer receive that list. One of the strengths of teaching a mechanistically organized course is that it facilitates explanations at critical points that prevent students from falling into misconceptions. For example, Joel and I recently discussed the value of having, in the chapter that introduces aromaticity, an explanation that the double bonds in benzene do not undergo reaction typical of nonaromatic double bonds. I supported Joel’s view that students need this type of information. As an example of other instructors’ interest in making this distinction, I cited a recent Journal of Chemical Education article that describes a demonstration that illustrates this difference in reactivity.
In addition, teaching a mechanistically organized course focuses on the “how” and “why” of organic reactions. This has made a difference. Students now regularly ask questions that allow me to discuss potential pitfalls. They now want to know why a step is unlikely to occur.
In fairness to students—and to offset the use of two exclamation points earlier—I’ll add that students cannot see organic chemistry the way instructors do. We are immersed in the subject and we enjoy it. In a sense, we keep taking the class over and over; certainly, we should be proficient. Our challenge is to bridge the gap between our expert experience and their initiation into the discipline.
— Steve Pruett