In organic chemistry, learners often find it difficult to derive implicit properties of functional groups involved in mechanisms. This is necessary, for example, to make appropriate predictions about the kinetics of a reaction. Linking explicit and implicit information or deriving causal relationships poses significant challenges to students and requires specific instructions to help them solve mechanistic problems. Yet, evidence-based instructional practices to promote mechanistic reasoning in organic chemistry are limited. Scaffolded case comparisons used in interview studies have been shown to foster students’ reasoning and to facilitate the processing of case comparisons in organic chemistry. However, it is still unknown if students with a differing level of concept knowledge equally profit from such a scaffold. To address this, we conducted a study with 18 participants in an Organic Chemistry II course who were asked to solve a scaffolded case comparison individually. Prior to this task, each learner completed a concept knowledge test and a cognitive ability test in paper-pencil format, as well as a second concept knowledge test after the task. Students’ working sheets were analyzed qualitatively, to determine the reasoning patterns that emerged in students’ usage of the scaffold, and quantitatively, to relate these patterns to students’ level of concept knowledge. Every student of the cohort could be assigned to one of five reasoning patterns, which differ in aspects of multivariate and causal reasoning. We illustrate how these reasoning patterns allow to diagnose students’ understanding, as well as design adaptive tasks.
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