The new year traditionally brings a time for both reflection and looking forward. For teachers of organic chemistry everywhere, this past year stands out more than most. After years of planning, MCAT-2015 is finally upon us. I previously wrote about the challenges and opportunities this change holds for us and how we, at Middlebury College, were planning to adapt. So as we greet 2015, it seems appropriate to reflect on how the first semester teaching our new organic chemistry curriculum with Joel’s textbook went and to see what lies ahead.
To recap, the main objective of our new curriculum was to prepare students to take biochemistry and eventually the MCAT after just one semester of organic chemistry (“Organic Structure and Reactivity”) without sacrificing the rigor necessary for those students continuing to the second semester of organic chemistry (“Organic Synthesis and Spectroscopy”). The key addition to the first semester course was about a month of carbonyl chemistry that came at the expense of spectroscopy and most synthesis considerations. Joel’s book, with its consistent emphasis on mechanism and process rather than outcome and memorization, was a key component of our plan (click to see our syllabus).
The first three weeks of the course we covered Chapters 1-5, which contain typical bonding, properties, conformations, and chirality. I was most impressed by the little things that made the textbook stand out. For example, it shows orbital correlation diagrams going from left to right, rather than left and right toward the center. The latter way is more conventional and perhaps makes better sense for more advanced users; however, I find that to be very confusing to most students. No other graphs or charts in chemistry are read that way, so showing hybridization and molecular orbital formation from left to right make it much more intuitive to follow.
Proton transfer reactions in Chapter 6 start off the mechanism-based curve arrow drawing, and the Chapter 7-9 trilogy on substitution and elimination reactions really kicks it into high gear. This was my first real point of concern when planning the course last year. Traditionally we have ended the first semester with this topic. However, starting off the study of reactions with SN1, SN2, E1, and E2 reactions proved outstanding. With the up front and explicit focus on mechanisms, students really bought into the plan to learn and understand rather than memorize the material. Students this term understood these much better than they have in the past. I saw the fewest number of “nonsense” mechanisms on our second exam that I have even seen. Even those students who could not get a problem correct were at least using the curved arrows correctly to try to do something reasonable. Joel’s keen insights into organic chemistry principles and mechanisms really showed in the way the text was written and presented throughout. Student focused on the “how” and “why” of organic chemistry much more than simply “what” and “when.”
With the first hurdle cleared, we plunged head-long into a month of carbonyl chemistry (chapters 17, 18, 20, and 21). Bypassing most of the synthesis and spectroscopy (chapters 10-16, and 19), proved almost a non-issue. We had to avoid a few end of chapter problems, but not that many. Putting most of the organic synthesis material in separate chapters (10, 13, and 19) really suited our new approach. Furthermore, the chapters that we did cover focused on the content at hand and not extensions of previous material that we had skipped.
For the students, carbonyl chemistry was indeed a bit of a challenge just half-way into their first semester of organic chemistry (vs. half-way through the second semester), but they really rose to the occasion. Led by the ever-present curved arrows and more fundamental organic chemistry principles, the carbonyl chapters really built quite nicely on substitution and elimination chemistry. Honestly, it was even better than I had hoped. We did skip over some sections here and there to stay focused on reactivity rather than synthesis. As before, this caused surprising little disruption to the flow of the course or the problems that students could do at the end of the chapters, which again were excellent practice that focused on process rather than outcome.
We spent the last two weeks of the course on special topics involving biomolecules and polymers. This was intended to be the bridge to biochemistry, but it also allowed everyone to see the reactions and mechanisms in a different context. For example, a day on fatty acid biosynthesis highlighted decarboxylation, the Claisen Condensation, carbonyl reduction, elimination, and transesterification. Amino acids and proteins brought together acid-base chemistry, resonance, intermolecular forces, and conformations. Two days on carbohydrates integrated chirality, stereoisomers, acetals, chair conformations, and the anomeric effect. It was wonderful! For the first time in 17 years students were more excited and enthusiastic at the end of the semester than the beginning of the term.
Looking forward, I think this group of students is better prepared for biochemistry than last year’s students who had a full year of organic chemistry. The students continuing to the second semester of organic (about a third of them) are also primed for success in our Synthesis and Spectroscopy course. It’s the best of both worlds. So, thank you MCAT for prompting us to innovate and redesign our curriculum—2015 is going to be a great year!
-Rick Bunt, Middlebury College