Arrows on the Page Are Not a Good Gauge: Evidence for the Importance of Causal Mechanistic Explanations about Nucleophilic Substitution in Organic Chemistry

Abstract

This three-year study builds on prior work analyzing students' causal mechanistic explanations about acid−base reactions. Here we extend that work to characterize and investigate how students construct causal mechanistic explanations of simple nucleophilic substitution reactions. After an initial pilot study, we adopted a modified version of the original task prompt which was used in two subsequent years to compare responses from students enrolled in a transformed organic chemistry course (Organic Chemistry, Life, the Universe and Everything) and a traditional organic chemistry course. Student responses were sampled in the middle of the first semester organic chemistry, just after they had learned the material, and once again at the end of the course, to identify how responses changed over time. Our findings from this study include (1) eliciting causal mechanistic explanations requires careful scaffolding to activate productive elements of a response, and (2) students from a transformed course are more likely to construct a causal mechanistic explanation at the end of Organic Chemistry 2 than students from the control group, suggesting that if students are to retain the use of valuable knowledge, this must be supported by instruction and course expectations.

Connecting Ideas across Courses

“…Together, these data support prior observations that while students can generally describe the role of energy in a simple, isolated system, applying that knowledge to a closely related phenomenon remains challenging (Cooper & Klymkowsky, 2013) and must be carefully scaffolded (Kararo et al, 2019;Crandell et al, 2020). Prior studies have shown that students similarly have difficulty in making spontaneous connections involving energy between disciplines (Nagel & Lindsey, 2015), and connections to biology may be particularly challenging to support given that biological phenomena are often highly contextualized (Opitz et al, 2019), as is the case here.…”

Techniques adopted in teaching students organic chemistry course for several years

“…(2020) In 2020, the act of learning organic chemistry focused on causal mechanistic arrows in substitution reaction (Crandell et al, 2020), the application of chemical structure teaching (CST) (Zheng et al, 2020), use of card game especially in learning functional group (Bell et al, 2020), and application of Posner's approach by implementing the design-based research technique (Kaanklao & Suwathanpornkul, 2020). Furthermore, it focused on the terminal object (TOs), and the development of specific students' capabilities (Betancourt-Pérez et al, 2020).…”

“…Organic chemistry is a difficult course, comprises of causal mechanistic arrows used to substitute the reaction or nucleophilic attack, which is the simplest type of organic reaction (Crandell et al, 2020). Moreover, high order thinking is needed in solving the problem reaction mechanisms and chemical principles (Flynn, 2014).…”

Scaffolding for chemistry students – which tools are assessed as being more helpful: stepped supporting tools or task navigators?

“…conclude that "it is a mistake to assume that students know how to approach the learning of organic chemistry because they have been successful in general chemistry". Therefore, while teaching organic chemistry, not only the content, but also learning strategies should be taught (Crandell, Lockhar, & Cooper, 2010). One possibility for guiding and therefore supporting students while learning chemistry is the use of suitable scaffolds.…”