"It's Only the Major Product That We Care About in Organic Chemistry": An Analysis of Students' Annotations of Reaction Coordinate Diagrams

The purpose of this study was to analyze organic chemistry students' annotations of reaction coordinate diagrams to better understand how they sought connections between reactions and reaction coordinate diagrams. Thirty-six students enrolled in Organic Chemistry II participated in semistructured, think-aloud interviews that asked students to choose a reaction coordinate diagram from a set of three possible diagrams to match a substitution reaction mechanism and then to match an elimination reaction mechanism. Students' annotations of the reaction coordinate diagrams provided in the interviews, and in some cases additional reaction coordinate diagrams generated by the students themselves, were examined. Qualitative analyses indicated that half of the participants considered only the "major" species (reactant, intermediate, and product) to be encoded in reaction coordinate diagrams, whereas the rest of the reaction species (leaving groups, nucleophiles/bases, and solvent molecules) were omitted from their drawings. These findings suggest that because organic chemists frequently write equations that are balanced neither in mass nor in charge, and because these equations tend to focus upon the formation of the major product, students can develop the idea that only the "major" chemical species are important to focus upon when interpreting the symbolic representations of reactions and reaction coordinate diagrams. The implications of these findings for classroom teaching are discussed.