Spectroscopy: Seeing (and Using) the Big Picture

Like many other instructors, I do the majority of spectroscopy instruction in my laboratory. It seems natural to integrate spectroscopy problems into lab exercises, and to use the molecules we make as the platform for understanding how to analyze them. Most organic texts I have seen introduce spectroscopy towards the end of the first semester (often after alkynes and before dienes). These chapters are somewhat self-contained, with an overview of theory and simple functional groups as examples. These chapters lend themselves to lab fairly easily, except for one major drawback: the simple functional group examples are….simple. Following the functional-group approach, each subsequent chapter highlights a functional group (ketone, carboxylic acid, etc.) with an introduction of physical and spectroscopic properties. While this was fine for reinforcing spectroscopy in lecture from lab, it was less than useful for laboratory. I want my laboratory to work alongside my lecture, and I don’t want to hold off on a reaction just because we haven’t officially learned how to analyze that type of product yet!

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Using Lab Reports to Reinforce the Mechanism

My students learn organic chemistry in a mechanistically organized course and I want to make sure they really understand how the mechanisms apply to reactions that are synthetically useful. There are many approaches that I use to reinforce their learning such as quizzes, practice problems, and SmartWork assignments. I previously talked about why I am a believer in using the lab portion of class to help reinforce the concepts covered in lecture. One important aspect is the reports assigned to each lab. I have found that students benefit from explaining how each mechanism works, using not just arrow pushing diagrams like on a quiz or practice problem, but also by being required to explain each step and aspect of the mechanism in their own words. This exercise forces them to demonstrate how much they truly understand.

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Mechanisms in Class, Mechanisms in Lab

I have always used a mechanistic approach when teaching organic chemistry. Every class I have taught, I started the first day saying, “Do you want to try to memorize hundreds, if not thousands, of individual reactions, or do you want to learn to understand how about ten reactions take place, so you can apply them to hundreds, if not thousands, of situations?” Inevitably, students always respond with the latter. Unfortunately, the way traditionally-organized texts are written encourages students to neglect their own preference and attempt to memorize reactions rather than understand them. Last year, I switched to Karty’s text because it laid out the concepts of organic chemistry the way I was already attempting to force another textbook to lay them out. The only challenge was organizing my lab to parallel this teaching approach.

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Playing Musical Chairs with Spectroscopy

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.

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Teaching the Mechanism Means Testing the Mechanism

Exam questions are a primary medium by which students learn what their instructor values most in the course. If we evaluate what we value, questions should test the mechanism and thus emphasize conceptual understanding, utilize real applications, and require deep thinking. And for me, the most important reason to pose mechanistic questions is to see how much students really know and understand.

Questions need not be completely different from more traditional exam questions but they must uncover why and how a reaction occurs, rather than just what occurs. When writing assessment questions for my course, ideas come from a variety of places. I often use the format of a question from Joel’s book or from Smartwork problems assigned for homework, while changing the context enough so that students can demonstrate that they understand the principles of the problem. I use questions students ask during office hours or study sessions as seeds for new assessment questions; if one student’s learning hinges on a given concept then others can probably learn from the question, too. Some exam questions I use are derived from clicker questions for which the majority of the class responded incorrectly, as I use these questions as opportunities to address misconceptions in class. The resulting exam questions allow me to measure student growth.

Here are some examples of questions I would have asked under a traditionally organized course and how they evolved for my mechanistically organized course:

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Solving the IR Puzzle

My three year old son recently has shown interest in solving puzzles. He dumps the pieces on the floor and randomly clicks them together until he finds a match. This is often the same approach that students take to problem solving in organic chemistry. To help my students work more systematically, I introduce IR early in the semester, as part of a laboratory experiment on the structural determination of an unknown solid, to model a strategic approach.

The strategy I introduce is both straightforward (there either are or are not absorbances that correspond to key functional groups) as well as creative and open-ended. Continue reading

Is Learning Organic Chemistry like Learning a New Language?

Over the years, I’ve heard many organic faculty use the phrase: “Learning organic chemistry is like learning a foreign language.” I’ve certainly used the phrase myself to give advice to my own students, in an attempt to convey that both subjects are cumulative and require a lot of practice. This year, however, I find myself rethinking this advice. This is because I’m currently taking introductory Italian here at Elon (yes, along with 22 undergraduates!) to prepare for my upcoming sabbatical at a research lab in Italy. With the unique perspective I’ve gained, I’ve found that, although there are some ways in which learning Italian and learning organic chemistry do align, there are significant limitations with the comparison. I now worry that making this comparison for students in organic chemistry could be misleading and could ultimately backfire.

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