Research in organic chemistry education has revealed that students often rely on rote memorization when learning mechanisms. Not much is known about student productive resources for causal reasoning. To investigate incipient stages of student causal reasoning about single mechanistic steps of organic reactions, we developed a theoretical framework for this type of mechanistic reasoning. Inspired by mechanistic approaches from philosophy of science, primarily philosophy of organic chemistry, the framework divides reasoning about mechanisms into structural and energetic accounts as well as static and dynamic approaches to change. In qualitative interviews, undergraduate organic chemistry students were asked to think aloud about the relative activation energies of contrasting cases,i.e.two different reactants undergoing a leaving group departure step. The analysis of students’ reasoning demonstrated the applicability of the framework and expanded the framework by different levels of complexity of relations that students constructed between differences of the molecules and changes that occur in a leaving group departure. We further analyzed how students’ certainty about the relevance of their reasoning for a claim about activation energy corresponded to their static and dynamic approaches to change and how students’ success corresponded to the complexity of relations that they constructed. Our findings support the necessity for clear communication of and stronger emphasis on the fundamental basis of elementary steps in organic chemistry. Implications for teaching the structure of mechanistic reasoning in organic chemistry and for the design of mechanism tasks are discussed.

Organic chemistry education is one of the youngest research areas among all chemistry related research efforts, and its published scholarly work has become vibrant and diverse over the last 15 years. Research on problem-solving behavior, students' use of the arrow-pushing formalism, the investigation of students' conceptual knowledge and their cognitive skills have shaped our understanding of college students' understanding in organic chemistry classes. This review provides an overview of research efforts focusing on student's perspectives and summarizes the main results and pending questions that may guide subsequent research activities.

If an organic chemistry student explains that she represents a mechanistic step because “it's a productive part of the mechanism,” what meaning could the professor teaching the class attribute to this statement, what is actually communicated, and what does it mean for the student? The professor might think that the explanation is based on knowledge of equilibria of alternative steps. The professor might also assume that the student implies information about how one of the alternatives influences the energetics of subsequent steps or how subsequent steps influence the equilibria of the alternatives. Meanwhile, the student might literally mean that the step is represented simply because it leads to the product. Reasoning about energetic influences has much greater explanatory power than teleological reasoning taking the consequence of mechanistic steps as the reason for their prediction. In both cases, however, the same backward-oriented reasoning is applied. Information about subsequent parts in the mechanism is used to make a decision about prior parts. To qualitatively compare the reasoning patterns and the causality employed by students and expected by their professor, we used a mechanistic approach from philosophy of science that mirrors the directionality of a mechanism and its components: activities, entities, and their properties. Our analysis led to the identification of different reasoning patterns involving backward-oriented reasoning. Participants' use of properties gave additional insight into the students' reasoning and their professor's expectations, which supports the necessity for clear expectations in mechanistic reasoning in organic chemistry classrooms. We present a framework that offers a lens to clarify these expectations and discuss implications of the framework for improving student mechanistic reasoning in organic chemistry.