Organic chemistry students’ interpretations of the surface features of reaction coordinate diagrams

Abstract

Organic chemistry students struggle with understanding the energetics of chemical reactions. Reaction coordinate diagrams are one tool that is widely used in organic chemistry classrooms to assist students with visualizing and explaining the energy changes that take place throughout a reaction. Thirty-six students enrolled in organic chemistry II participated in a qualitative study that used semi-structured interviews to investigate the extent to which students meaningfully extract and integrate information encoded in reaction coordinate diagrams. Results show that students have difficulties explaining the meanings of surface features such as peaks, valleys, peak height, and peak width. Analysis of students’ explanations resulted in four themes that describe students’ challenges with correctly interpreting the features of reaction coordinate diagrams. Students conflated transition states and intermediates, despite being able to recite definitions. Students described the chemical species encoded at points along thex-axis of the reaction coordinate diagrams, while largely ignoring the energies of the species encoded along they-axis. Implications for teaching organic chemistry are discussed.

Considering alternative reaction mechanisms: students’ use of multiple representations to reason about mechanisms for a writing-to-learn assignment

“…Studies in the literature also examine students' understandings of RCDs with investigations into how students interpret the meaning of RCD surface features (Lamichhane et al, 2018;Popova and Bretz, 2018a, 2018b, 2018cAtkinson et al, 2020. The studies by Popova and Bretz (2018a, 2018b, 2018c specifically report several findings about how organic chemistry students understand RCDs.…”

“…Studies in the literature also examine students' understandings of RCDs with investigations into how students interpret the meaning of RCD surface features (Lamichhane et al, 2018;Popova and Bretz, 2018a, 2018b, 2018cAtkinson et al, 2020. The studies by Popova and Bretz (2018a, 2018b, 2018c specifically report several findings about how organic chemistry students understand RCDs. For example, Popova and Bretz (2018a) identified that students in their study often viewed RCDs as encoding information that reflects only the major reacting species rather than all components of a reaction, often not considering the submicroscopic level.…”

“…They also found students have difficulty with this task because their reasoning with the mechanisms was often productoriented and focused on the surface features of reactants (Popova and Bretz, 2018b). The Popova and Bretz articles (2018a, 2018b, 2018c were all in the context of a course that primarily taught RCDs alongside reactions in first-semester organic chemistry (e.g., substitution, elimination, and addition reactions) but not in the second semester of instruction. Hence, their findings suggest the need to provide students with further opportunities to develop their reasoning with RCDs.…”

Research on Students' Understanding of Michaelis-Menten Kinetics and Enzyme Inhibition: Implications for Instruction and Learning

“…In the final paper published for this project, themes were discussed related to how students described the Michaelis-Menten graph, Lineweaver-Burk plot, and reaction scheme (i.e., E þ S ES E þ P) (70). With respect to the Michaelis-Menten graphs, it was noted that 4 of the students in the sample implicitly or explicitly attributed time to the x-axis, with similar results discussed in other research related to students' understanding of reaction coordinate diagrams (17). More broadly in the mathematics education community, research has also noted students' tendency to impose time on functions not involving time (18).…”

“…Focusing more specifically on mathematical models such as graphs across the physical sciences, interpreting the information provided in a graphical representation is complex, with mathematical ability and contextual complexity serving as potential barriers for students (12)(13)(14)(15). Moreover, students tend to focus on and cue into surface features of graphs, such as an overemphasis on the shape of the graph (16) or inappropriately attributing time to the x-axis (17). There is a similar trend observed in the mathematics education research literature, in which students impose time on functions that did not have time as the independent variable (18).…”