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

Abstract

Reaction mechanisms are central to organic chemistry and organic chemistry education. Assessing understanding of reaction mechanisms can be evaluated holistically, wherein the entire mechanism is considered; however, we assert that such an evaluation does not account for how learners variably understand mechanistic components (e.g., nucleophile, electrophile) or steps (e.g., nucleophilic attack, proton transfer). For example, a learner may have proficiency of proton transfer steps without sufficient proficiency of a step where a nucleophile and electrophile interact. Herein, we report the development of a generalized rubric to assess the level of explanation sophistication for nucleophiles in written explanations of organic chemistry reaction mechanisms from postsecondary courses. This rubric operationalizes and applies chemistry education research findings by articulating four hierarchical levels of explanation sophistication: absent, descriptive, foundational, and complex. We provide evidence for the utility of the rubric in an assortment of contexts: (a) stages of an organic chemistry course (i.e., first or second semester), (b) across nucleophile and reaction types, and (c) across prompt variations. We, as well, present a case study detailing how this rubric could be applied in a course to collect assessment data to inform learning and instruction. Our results demonstrate the practical implementation of this rubric to assess understanding of nucleophiles and offer avenues for establishing rubrics for additional mechanistic components, and understanding and evaluating curricula.

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

“…Several analogous variations of constructed-response items have been reported in the literature for prompting learners to describe what is happening and why for a range of reaction mechanisms Sevian and Talanquer, 2014;Cooper et al, 2016;Caspari et al, 2018a;Crandell et al, 2018Crandell et al, , 2020Dood et al, 2018;Bode ´et al, 2019;Graulich et al, 2019;Deng and Flynn, 2021;Kranz et al, 2023;Yik et al, 2023). While not exclusive to such purposes, these constructed-response items have been presented for use as formative assessments, for promoting learning, and for instructors to respond in real time to the measured learning (Dood et al, 2018(Dood et al, , 2020aYik et al, 2021).…”

“…In developing a rubric to evaluate the level of explanation sophistication for nucleophiles (herein referred to as the nucleophile rubric), Yik et al (2023) reported modifications of a reasoning framework preposed by Dood et al (2020a). The nucleophile rubric includes an Absent level (i.e., a non-normative or no explanation level) not found in the other frameworks reviewed by Dood and Watts (2022a); a possible reasoning for why such a level has been excluded is that prior frameworks tended to be research-focused while the work by Yik et al (2021) focused on developing an assessment tool for instructors and learners to use.…”

“…The nucleophile rubric includes an Absent level (i.e., a non-normative or no explanation level) not found in the other frameworks reviewed by Dood and Watts (2022a); a possible reasoning for why such a level has been excluded is that prior frameworks tended to be research-focused while the work by Yik et al (2021) focused on developing an assessment tool for instructors and learners to use. An absence of understanding can be evaluated in responses to formative assessment constructed-response items using the framework from Yik et al (2023). The nucleophile rubric also has Descriptive, Foundational, and Complex levels with increasing sophistication wherein the Descriptive level maps onto the teleological and anthropomorphic aspects of reasoning and the Complex level maps onto causal mechanistic reasoning.…”

“…In other words, a sound Complex level of explanation sophistication could contain teleological reasoning or anthropomorphism as long as a causal mechanistic explanation was part of the explanation. Fundamentally, the choices made by Yik et al (2023) communicate that the audience for their rubric (i.e., reasoning framework) are instructors and learners, and therefore demonstrate that their reasoning framework is intended for audiences beyond reasoning researchers. The work reported herein extends upon Yik et al (2023) with analogous levels of explanation sophistication focused on electrophiles.…”

“…Fundamentally, the choices made by Yik et al (2023) communicate that the audience for their rubric (i.e., reasoning framework) are instructors and learners, and therefore demonstrate that their reasoning framework is intended for audiences beyond reasoning researchers. The work reported herein extends upon Yik et al (2023) with analogous levels of explanation sophistication focused on electrophiles.…”