Impact of Assessment Emphasis on Organic Chemistry Students’ Explanations for an Alkene Addition Reaction

• Kimberly S. DeGlopper ^[1] ; Cara E. Schwarz ^[1] ; Niall J. Ellias ^[1] ; Ryan L. Stowe ^[1]
  1. [1] University of Wisconsin−Madison, United States
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 99, Nº 3, 2022, págs. 1368-1382
• Idioma: inglés
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• Resumen

  • To potentially engage students in “doing organic chemistry”, organic chemistry courses should foreground weaving together structure- and energy-related ideas to construct causal accounts for phenomena. Here, we investigate whether enrolling in an organic chemistry course that places substantial emphasis (∼50% of total points) on explaining phenomena on exams is associated with more productively justifying the outcome of a chemical process. This work occurred in the context of three learning environments that differed principally by assessment emphasis. The “explanation focused” course allotted 40–66% of points on exams to explaining phenomena while the other two enactments placed much less emphasis on connecting big ideas to how and why chemical processes occur (∼0–25% of total points). Students enrolled in each course were given a prompt which asked them to draw mechanisms for a hydrobromination reaction and subsequently justify the regiochemical outcome of that reaction. We described student responses by noting the connections made between structure (of reactants, intermediates, transition states, or products) and energy. Most students described how charge or electron delocalization impacted the relative energies of the two possible intermediates or transition states. Other explanations invoked steric repulsion or differences in relative energy due to the degree of carbocation substitution. An examination of the association between learning environment enrollment and explanation code distribution revealed that students who enrolled in two semesters of an explanation-focused course were substantially less likely to leave out charge delocalization in their explanations while students who were never enrolled in the explanation-focused learning environment were substantially more likely to leave out charge delocalization. These findings suggest that changing what is assessed to better align with “doing organic chemistry” may be a promising avenue for reform.