Exploring Student Thinking About Addition Reactions

While student reasoning about many of the reaction types covered in the organic chemistry curriculum have been studied previously, there is minimal research focused specifically on how students think about the mechanisms of addition reactions. This study addresses that gap by probing organic chemistry students’ thinking using think-aloud interviews as they worked through two different addition reactions. Students worked through the mechanisms using either paper and pencil or an app that dynamically represents the molecules. Overall, students were able to identify the steps of the two addition reactions but did not always successfully apply chemical thinking during the mechanistic steps. Specifically, both groups of students struggled with the concepts related to carbocation stability, frequently misapplying stabilization via substitution and demonstrating difficulty in identifying the potential for resonance stabilization. Our results suggest that instructors should emphasize the conceptual grounding directing mechanistic steps, in particular when determining carbocation stability.