For years I told my students they shouldn’t merely memorize a list of reactions. But what were my actions really telling them?
In the last textbook I used, the alkene chapter began with nomenclature, then covered Markovnikov addition of H-X and water, halogenation and halohydrin formation, and ended with hydroboration/oxidation. The next chapter that covered alkynes follows a similar path: nomenclature, Markovnikov addition of H-X and water, hydroboration/oxidation, but finished with formation and reaction of the acetylide anion.
I always told my students (and still do) to look for patterns. Organic chemistry is more a pattern-recognition course than memorization or algorithm-based. But what patterns were my students supposed to see in these chapters? The common theme was “reactions of ____ functional group.” Alkenes do a bunch of reactions, but each new mechanism is different from the last. It looks like alkynes do some similar reactions, but their products don’t always follow the alkene pattern. Plus, the alkyne can be made into an SN2 nucleophile. Epoxides wouldn’t be formed until a later chapter.
It’s hard not to feel sympathy for the student who feels that memorizing is the only chance at survival.
At Butler, we have four learning goals for our students in organic chemistry: to learn the language, drawing style, and three-dimensional structure of organic molecules; to know and apply organic reactions; to demonstrate understanding of reaction mechanisms; and to integrate this knowledge through synthesis. Of these learning objectives, the most difficult for students to embrace is synthesis. For many of them, this is the first time they have been asked to apply new knowledge at the college level. While we recognize that very few of our students are likely to become synthetic chemists, we feel that synthesis is a valuable intellectual tool to facilitate creative problem solving.
For longer than the 14 years I’ve been at Elon University, we’ve been administering the full-year ACS final exam in organic chemistry at the end of spring semester. It’s a valuable tool to assess our effectiveness in teaching the fundamental material that students are expected to know, and it also lets us see how our students stack up against students from across the country. In fact, the yearlong ACS exam was one of the assessments I used to assure myself that teaching under a mechanistic organization was better for students (see my previous post). That exam remained relevant for my course after I switched because, after all, the content I was teaching didn’t change; only the order in which it is presented did. But what about the first-term ACS organic exam? How does it fit with a mechanistically organized course? Now that I’ve been administering the first-term ACS exam in my organic classes for a few years, I have some answers to a few specific questions that tend to come up.
I had been going through Ken Bain’s What the Best College Teachers Do with a new faculty member this semester. The overarching theme of Bain’s book is that the best college teachers are student-centered. These “best teachers” are constantly trying to get into students’ heads to help them learn how to learn. It is not about the material or the test; it is about helping the students grow synapses to make them better problem solvers, no matter the content or subject.
Of course, I think of myself as attempting to do that but I never thought the textbook really had much to do with it. After reading Bain’s book, I thought about Joel’s book in the context of this idea and I realized a textbook can be a real asset or a real impediment to this approach. Joel’s text is the former. It is focused on the core of what organic chemistry is all about. Someone recently asked for my impression of the text and I thought to myself “It’s no Streitwieser.” That’s when it hit me. No, it’s not Streitwieser, and that is a really good thing.
I did not realize my commitment to traditions—in my personal life and in the classroom—until recently. In my personal life, I discovered that I was married to a person who did not know that: Christmas trees are decorated while listening to Christmas music and not with a basketball game on in the background; salads are eaten after the main meal; there is no TV in the morning; and soda is a restaurant-only drink. In the classroom, my closely-held tradition was to introduce free radicals first. Traditions are fine, important things, which is why we observe them. But at what point do we rethink traditions? Are we traditionalists open to new, improved ideas?
Mechanisms can greatly simplify organic chemistry thereby allowing us to draw connections between reactions that might otherwise appear to be unrelated. With some reactions, however, I have found that the way in which the mechanism is presented can have a dramatic effect on whether a student successfully makes these connections. Consider, for example, the halogenation of an alpha carbon. The mechanism under basic conditions is often presented as in Scheme A here:
I taught this mechanism this way for several years, but I noticed that many of my students struggled with it. I recently made some changes to how I present this mechanism—in class and in my textbook—that seem to have benefited students significantly. What makes this mechanism difficult for some students to handle? And what were the changes I made?
Two-cycle organic chemistry is a pedagogical approach that has gained in popularity over the last couple decades. It’s a rather simple idea: The first semester course is treated as something of a survey, dealing primarily with the fundamentals, whereas the second semester revisits many of the same topics from the first semester, but treating them in greater depth. This two-cycle approach seems to be particularly advantageous for institutions whose biology majors (and other nonmajors) are required to take just one semester of organic chemistry. With less depth in each first-semester topic, nonmajors are exposed to more topics, and the material, moreover, can seem less intimidating. For chemistry majors and pre-health students, a significant benefit might come from the way that second-semester material is treated. Revisiting the first semester topics in greater depth represents an inherent review of the earlier material, allowing students to stay fresh on that material throughout the entire year. And because the second semester maintains a focus on the more challenging material, students should be better prepared for the final exam.
Despite these potential benefits, instructors who teach (or want to teach) a two-cycle organic course face a significant problem: Which book to use. Continue reading →