Do Your Students “Get” Aldol Reactions?

As a new professor, I had mixed feelings about spring break. On the one hand, I was so ready for a vacation, but on the other, I remembered what it was like as a student that time of year. Your mind is on anything but classes. Not only are you looking forward to a week at the beach (or at least anywhere but campus), but you’re also starting to see summer on the horizon. For organic students who have made it through a semester and a half of a tough subject, it’s easy to understand why many of them “check out.” That’s why I felt a bit apprehensive about scheduling exam two the Friday after my students returned from break. Not only was I asking them to jump right back into organic full swing, but the material we had covered for this second exam was definitely not trivial (not that there is really a “trivial” chapter in organic!).

Exam two covered chapters 17-20 of Principles and Mechanisms, and if you’re familiar with the textbook, you know this is quite a bit of material. However, we got through the exam with few complaints. A few days later, I entered the grades into the grade book and started to suspect that I’d done something wrong. The average for this test was about 5% higher than any of my previous exams throughout the year. While there could be multiple contributing factors for this jump in scores, I can’t help but attribute most of it to the hard work of my students and the success we’ve seen with a mechanistically organized course.

Throughout the semester, I’ve seen my students become stronger and stronger in their understanding of organic chemistry. This is really wonderful, especially as a lot of people might argue that Organic II is the harder semester. Its difficulty is in large part due to the sheer volume of material that is covered as the students ultimately learn dozens and dozens of unique reactions. I’ll focus here on Aldol-type reactions as this was the focus on test two.

As an undergraduate I remember Aldol-type reactions feeling a bit daunting. We were expected to learn multiple different reactions and the unique aspects that set each reaction apart. By concentrating on mechanisms, my students this semester are learning the same reactions and are instead focusing on what makes each of them so similar. With this understanding, we can then discuss how small differences, like the relative pKa of the alpha proton or the electrophilicity of the carbonyl, can impact the outcome of seemingly identical reactions. Take the Robinson Annulation as an ideal example. At first glance this reaction looks complicated and messy and students think the mechanism will be impossible to learn. When we break it down, they realize they already know that the stabilized carbon nucleophile (the enolate) will attack the alpha beta unsaturated carbonyl via conjugate addition—just like we saw in the previous chapter. With the product of that reaction in hand, it’s easy to see how an intramolecular Aldol condensation will come next, and before you know it, you’re done.

The best part about teaching a mechanistically organized course is that when I need to introduce a completely new topic…it’s not really new. I can easily break it down into the bits and pieces that match what we’ve already seen. That takes a lot of the pressure off of me as I teach, and it also lets the students enter each new chapter with more confidence. They know that even though we’re moving through new material, we’re really just building on the foundations we’ve been strengthening since the beginning of first semester. As we complete chapters ahead of schedule, I’ve been able to challenge my students with more in-depth problems that would normally be reserved for a problem set, and only discussed in-depth if the students venture in to office hours. By adding these to an in-class discussion, I can reach more students with tougher problems. In turn, the students and feel more confident going in to the exam. I still feel like I can add challenging problems to exams, but I see my students find them less and less daunting as we progress through the semester.

I have to say that as a new professor, teaching from a mechanistic viewpoint has been a lifesaver. Ultimately, those of us that love organic chemistry love it in part because we can look at a brand new reaction and predict the outcome based on a few fundamental concepts. As a new professor, teaching this to a class of terrified underclassmen is an intimidating task. We don’t have the benefit of years of experience tweaking our lesson plans and playing around with the order in which we teach the chapters. Having the material pre-organized for me has helped tremendously.

-Jamie Ludwig, Elon University

Click here to learn more about Prof. Ludwig.

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