It’s my favorite time of the year. Finally, we get to do chemistry in organic chemistry! Not to malign BDE, IMF, chair vs. boat conformations, etc., but I have always thought of the stuff leading up to this point—strains and conformers, the designation of stereochemistry and the terms and rules associated with their nomenclature—a bit of a molecular card game. Though important, it’s just a bunch of rules, names, and designations so chemists can speak with other chemists. Chapters 6 and 7 introduce students to real applications of chemistry. It seems like a lot of information to throw at them but it works well.
We started Chapter 9 in class a couple weeks ago, where we learn how to predict the outcome of the SN1/SN2/E1/E2 competition. Similar to how it’s done in most books, we do this by first learning about the major factors that influence the rate of each reaction in this competition. But unlike other books, this is not where students encounter some key, challenging aspects of these reactions for the very first time. Rather, students will have had significant exposure to some of these major factors, like solvent effects, from earlier in the book. Because students revisit these ideas in Chapter 9 as opposed to learning them anew, I can focus much more tightly on the topic at hand: the competing reactions. My students come away with a better handle on things and are able to predict the outcome of this competition more effectively than they have in years prior.
I have been teaching organic chemistry for a long time (several years ago I had a wonderful student who pointed out that I taught her dad!). The beginning of first semester of organic chemistry is always clunky and sometimes even painful. How does one make it through the first class without going through every detail that the students faithfully learned in general chemistry, while taking into account that their memory of general chemistry is more wobbly than a fresh batch of Jell-O? What new material can be introduced? Adding to the confusion is the lack of a common language needed to go forward in the course.
In my textbook, resonance is presented rather extensively in Chapter 1 (“Atomic and Molecular Structure”), ultimately teaching students how to draw all resonance structures of a given species. I like to teach resonance to that depth early in the course because it reinforces topics that are vital to student success throughout the entire year of organic chemistry: the octet rule, formal charge, and curved arrow notation. Because each new resonance structure requires valence electrons to be rearranged, each time students draw a resonance structure, they must re-consider whether an atom’s octet has been exceeded, and must also re-valuate the formal charges on atoms. And to properly indicate how to move those valence electrons, students must develop a working knowledge of curved arrow notation—the same curved arrow notation that will facilitate their mastery of reaction mechanisms later on. When it comes to practicing these important aspects of organic chemistry, the earlier and more frequent the better.
Of all the chapters in Joel’s mechanistically organized textbook, my favorite is Chapter 6: The Proton Transfer Reaction. Acid-base chemistry might seem like an odd topic to pick in an organic chemistry textbook. It seems almost…inorganic, a throwback to general chemistry of sorts. So why do I like it so much? It accomplishes two vitally important tasks that have big pay offs for the rest of the year.
As a Synthetic Organic Chemist by trade, I use NMR spectroscopy heavily for analysis and structure identification. When designing a course in organic chemistry, it comes as no surprise that I want my students to be comfortable mining information from an NMR spectrum and using it to solve problems. A mechanistically organized course lends itself well to teaching spectroscopy early, both for organizational and conceptual reasons.
Shortly after I began teaching, when I was still using a book organized by functional group, I came to dread the second exam of the first semester. The class would typically perform decently well on the first exam, but scores would plummet on the second one. I recently looked back at my records for a reminder: the final year I taught from that functional group book, the class averaged 72 on exam one and 60 on exam two. For lack of a better description, exam two would crush my students. I remember wondering if this issue was something specific to me and how I taught. But after talking with my organic colleague at the time, who was a seasoned veteran, I learned that this was a regular trend at my institution since long before I arrived. If it wasn’t just me, what was the problem?