Organic Chemistry Students’ Understandings of What Makes a Good Leaving Group

Abstract

Thirty-six students enrolled in Organic Chemistry II participated in individual, semistructured, think-aloud interviews about the factors that contribute to the stability and reactivity of organic species in the context of unimolecular and bimolecular nucleophilic substitution and elimination reactions. The students were provided with the mechanistic steps for these reactions. Most students correctly identified the leaving groups in these reactions and referred to them as “good leaving groups”. However, less than half of the students could explain the electronic and structural factors that justify characterizing a species as a “good” leaving group. Nearly one-third of the students who were interviewed were unable to provide any explanation of what factors result in a chemical species being a “good” leaving group. These findings are discussed through the lenses of both Perry’s scheme of intellectual development and Ausubel and Novak’s theory of meaningful learning.

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

“…Such work should be built using the vast array of literature that exists regarding student understanding of organic chemistry reaction mechanisms. 26,27,[64][65][66][67][68][69][70] For example, research findings related to student understanding of other reaction types and components of reactions (e.g., nucleophiles and electrophiles, 71,72 leaving groups 73 ) could be used to develop additional tutorials.…”

Using the Research Literature to Develop an Adaptive Intervention to Improve Student Explanations of an SN1 Reaction Mechanism

“…It has been reported in the literature that students describe leaving groups as "good leaving groups" but are unable to explain why a leaving group is "good." 1,7 Popova and Bretz 7 saw students simply reciting examples of "good" and "bad" leaving groups, unable to explain the factors which led to this leaving group ability. To encourage students to develop deeper explanations of leaving group ability, Popova and Bretz recommended requiring students to provide written explanations of their work and learning activities that encourage students to use multiple factors to solve problems, fostering a shift away from dualistic thinking.…”

“…As Popova and Bretz noted, in order to predict leaving group ability, students must be able to predict relative acid/base strength by understanding factors that impact basicity; for example, atomic size and electronegativity. 7 The Level 2 Tutorial similarly states the periodic table trends for size and electronegativity but focuses more on polarizability as the reason for the better leaving group ability of larger atoms. The unit defines polarizability as "the ability to distribute electron density unevenly in response to external forces."…”

The E2 mechanism: β‐eliminations at haloalkanes – New model experiments for concept learning in teacher training

“…Wie oben bereits erwähnt, spielt für E2‐Reaktionen wie für S N 2‐Reaktionen die Qualität der Abgangsgruppe eine wichtige Rolle. Ist diese Thematik, die bei Studierenden neuesten Arbeiten zufolge mit erheblichen Fehlvorstellungen verknüpft ist [12], im Zusammenhang der S N 2‐Reaktionen bereits hinreichend bearbeitet worden [13], können Lernende dieses Wissen bei E2‐Reaktionen unmittelbar anwenden. Ferner stimmt auch die Molekularität von E2‐ und S N 2‐Reaktionen überein: Beide Reaktionen sind bimolekulare Elementarreaktionen.…”