Development and evaluation of a Lewis acid–base tutorial for use in postsecondary organic chemistry courses

Abstract

A well-developed understanding of the Lewis acid–base model is highly important for the understanding of organic chemistry. As such, students should receive instruction and be assessed on use of the model. Online tutorials and constructed-response items provide a means for confirming that students have a well-developed conceptualization of the Lewis acid–base model. In a prior study, a predictive logistic regression model was presented that can be used with constructed-response assessment items to determine use of a Lewis acid–base model in written responses. In this study, we use that predictive model to evaluate the effectiveness of a tutorial designed to promote meaningful understanding of the Lewis acid–base model in three different instructional contexts: first-semester organic chemistry students before summative assessment, first-semester organic chemistry students after summative assessment, and second-semester organic chemistry students. Additionally, we evaluated the learning gains of one set of first-semester students after a 3-week time delay. McNemar’s test results suggest that the tutorial had a net positive impact in all three instructional contexts, with the most significant impact observed with the second-semester students. This work has implications for further development of literature-based tutorials to promote meaningful understanding of organic chemistry reaction mechanisms assessed by constructed-response items.