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

Abstract

Organic reaction mechanisms are often represented by the electron-pushing formalism and reaction coordinate diagrams. These representations pose a challenge to students because valuable information is encoded within each representation, and students must know how to reason about mechanisms using both. Hence, it is important to understand whether and how students consider these two representations when reasoning about reaction mechanisms. We have collected responses to a writing-to-learn assignment administered in a second-semester organic chemistry laboratory course to investigate students’ reasoning. The assignment was designed to elicit students’ reasoning about the most likely of two mechanisms for a catalyzed intramolecular aldol reaction when given the electron-pushing scheme and reaction coordinate diagram for both mechanisms. As part of the assignment, students submitted initial drafts, participated in content-focused peer review, and submitted revised drafts. We analyzed each component using a mixed methods approach to identify students’ reasoning about the most likely reaction pathway and how their reasoning changed after peer review and revision. In this article, we present a quantitative overview of changes students made about their decisions for the most likely reaction pathway and how these changes are related to providing and receiving feedback. Additionally, we present our analysis of the features of representations students used to reason about the likelihood of alternative reaction mechanisms. This study demonstrates how existing research about students’ reasoning with representations was operationalized for classroom practice using writing-to-learn. Furthermore, the analysis illustrates how writing-to-learn to can be used to develop students’ reasoning and offers implications for teaching students to reason about reaction mechanisms using multiple representations.

Evaluating electrophile and nucleophile understanding: a large-scale study of learners’ explanations of reaction mechanisms

“…Prior work has shown a disparity between how electrophiles and nucleophiles are identified and described in various contexts with a particular reliance on explicit structural features (Bhattacharyya and Bodner, 2005;Strickland et al, 2010;Bhattacharyya, 2014;Bretz, 2015, 2016;Graulich, 2015;Akkuzu and Uyulgan, 2016;Putica and Trivic, 2016;Galloway et al, 2017;Caspari et al, 2018a;Dood et al, 2020a;Watts et al, 2020Watts et al, , 2022Dood and Watts, 2022b). Bretz (2015, 2016) found that learners were more apt at identifying and providing examples of electrophiles and nucleophiles when charge was explicit: for example, the positive carbon in a carbocation species or the negatively charged oxygen of an alkoxide.…”

“…At the heart of such difficulty is translating the representational system for chemical structure and reaction mechanisms (i.e., the electron-pushing formalism) into nuanced understandings (often implicit features) of electron deficient and electron sufficient atoms and moieties. While electrophiles and nucleophiles are paired, the research literature suggests that learners have a differential understanding of the two, with more proficiency associated with identifying and describing nucleophiles Bretz, 2015, 2016;Galloway et al, 2017;Caspari, et al, 2018a;Graulich et al, 2019;Watts et al, 2020Watts et al, , 2022. At present, chemistry education researchers in this area have primarily used in-depth interviews to explore learners' understanding of organic chemistry topics.…”

Generalized rubric for level of explanation sophistication for nucleophiles in organic chemistry reaction mechanisms

“…As Cooper and others have argued, learners must have opportunities to demonstrate and wrestle with any outcome or objective we seek through our instruction (Cooper, 2015;Becker et al, 2016;Stowe and Cooper, 2017;Bode ´et al, 2019;Galloway et al, 2019;Watts et al, 2020Watts et al, , 2022. In other words, if we want learners to ascribe meaning to reaction mechanism drawings, then we must ask learners to communicate that meaning, e.g., through written explanations.…”

Reading textual and non-textual explanations in chemistry texts and textbooks – a review

“…Representational competence refers to ''a set of skills and practices that allow a person to reflectively use a variety of representations or visualizations, singly and together, to think about, communicate, and act on chemical phenomena in terms of underlying, aperceptual physical entities and processes'' (Kozma and Russell, 2005, p. 131). Representational competence has frequently been of interest in chemistry education research (Atkinson et al, 2021;Parobek et al, 2021;Popova and Jones, 2021;To ´thova ´et al, 2021;Watts et al, 2022) and has been considered when evaluating the effect of representations on students' learning (Larkin and Simon, 1987;Hsu and Yang, 2007;Ariasi and Mason, 2014;Enero Upahi and Ramnarain, 2019;Gkitzia et al, 2020).…”

“…For chemistry, education research also focuses on specialised forms of representations like symbolic language features of the language of chemistry (Taber, 2015;Liu and Taber, 2016) or mechanistic language features in organic chemistry (Bongers et al, 2019;Watts et al, 2022). Research by Bhattacharyya (2014), Galloway et al (2017) and Graulich and Caspari (2021) outline differences of students' reading and interpretation of mechanistic language in chemistry and spectra are evaluated in terms of reading texts on the tertiary level (Topczewski et al, 2017;Connor et al, 2021).…”