By Michael Wirtz, Assistant Head of School/Science Faculty

“Negative finds the positive.” I use this phrase often. If you did not know me, you might think I was a pessimist. In fact, I am quite the opposite: I am a teacher and I believe that optimism lies at the core of any good teacher. I share this phrase, “negative finds the positive,” in my attempt to distill the complexities of organic chemistry[1] into something sticky for my students. While most chemistry students experience limited amounts of organic chemistry in high school, it is a discipline featured prominently in my Advanced Chemistry course at St. Mark’s. In fact, organic chemistry is critical to the narrative of the course, helping my students and me to seek deeper understandings of the broad discipline of chemistry. Organic chemistry is our yearlong storyline. And like all stories, there are characters, action, and a plot.

The course’s narrative begins with the backstory where we tease out issues of structure, order, and symbolism. Nature relies on low energy systems to create order. Water flows downhill and eventually into larger bodies. In chemistry, high energy atoms combine to create larger, more stable (i.e. lower energy) molecules. Molecules can be hugely complex, an interconnected system of atoms with properties different from the component parts. Humans simplify these systems and the orders they create with symbols, some as simple and familiar as H₂O and as complex as

Source: http://en.wikipedia.org/wiki/Varenicline

Just as in the analysis of a novel, it is critical for students to find and understand these symbols for the more complex picture they are creating. With the symbols called out, we can unpack them further as we move deeper into the narrative. Molecules are built through the movement and sharing (or transfer of) electrons – infinitely small and negatively charged particles – due to their attraction to slightly positive centers resulting in a bond; negative found a positive. The storyline comes into resolution.

A narrative is often propelled by the actions of its characters. Organic chemistry is no exception. The characters – the molecular and charged systems created as symbols previously – begin an organized choreography, described by “curved arrow notation.” Like the central theme of a great work of literature, “negative finds a positive” re-emerges as we employ curved arrow notation, a symbolic human construct created to explain the un-seeable. Using this notation, the breaking and creating of new bonds are articulated; the tails of arrows indicate the source of electron density (“the negative”) and point to electron deficient centers (“the positive”). This work also foreshadows learning yet to come, even as it creates new characters and yet more action:

Source: http://www.chem.sc.edu/faculty/shimizu/333/Chem_333/1c.iii.html

Action is not enough to make a story compelling, however. The most interesting narratives have both action and a tension. The characters in our organic narrative are motivated by myriad factors, giving rise to dynamic equilibria. In its simplest form, equilibrium is a competition between the forward and reverse chemical reactions. Applied to organic chemistry, equilibria are often a tug-of-war between species in a chemical reaction that are pushing and pulling on a hydrogen atom. The negative finds a positive to which it wants to hold firmly.

The forces behind the scenes add rich layers of complexity and drama. The rate of the reaction and the energy concerns are major factors in the outcome of the story. Which force will dominate: speed (“kinetics”) or energy considerations (“thermodynamics”)? All reactions are not created equal in these ways, allowing for points of comparison and deep analysis as we unpack the narrative. In the midst of kinetics and thermodynamics, the course spirals back to curved arrow notation and substitution reactions, topics from early in the year return. We revisit these earlier topics and unearth new perspectives and complexities not apparent in the first encounter. The plot thickens and the idea of “negative finds a positive” returns once more.

The idea of narrative and of telling the story of chemistry has always appealed to me and fit my view of the field. As a teacher, I want to create the conditions for my students to engage readily with the course and develop lifelong skills through the vehicle of the course content. By creating a course with a strong narrative component, I am able to tap into something critical to the human experience. We tell stories to entertain, to transmit knowledge, and to build connections. There is power in this history and I attempt to draw from it in pursuit of deeper learning opportunities for my students. Organic chemistry creates a platform that entertains, transmits, and connects my students to the broader discipline of chemistry, turning a potential negative into a positive.

Michael Wirtz is in his fifth year at St. Mark’s in the role of Assistant Head/Dean of Faculty. He also teaches AP Chemistry and is leading the School’s STEM initiative.

[1] Organic chemistry is the study of the structure, properties, and reactivity of the compounds of carbon. These compounds often contain other atoms, most notably H, O, N, and members of the halogens. Organic compounds are incredibly important and prevalent in our lives, from biological and industrial processes to petroleum products to pharmaceutical agents.