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E-/Z-, But Not Easy


Frank J. Dinan
Department of Chemistry & Biochemistry
Canisius College


In this case study, two students meet a professor who surprises them by telling them that a biochemically important molecule’s structure has been incorrectly represented in the published literature - in an article in the Proceedings of the National Academy of Sciences, a major biochemistry textbook, and even The Merck Index. The students are challenged to find the nature of the structural errors and correct them. In addition to demonstrating that the technical literature is not without its flaws, the case reviews important concepts related to geometric isomerism and tautomerism.

  • To get students to think critically about the literature sources they use in chemistry.
  • To review concepts related to geometric isomerism and tautomerism.
Keywords: Bilirubin; Z-isomer; E-isomer; geometric isomerism; Cahn-Ingold-Prelog; tautomerism; scientific literature
Topical Area: N/A
Educational Level: Undergraduate lower division
Formats: PDF
Type/Method: Directed
Language: English
Subject Headings: Organic Chemistry   Biochemistry  
Date Posted: 10/17/03
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

Teaching Notes

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I have used this case with my Organic Chemistry II class. Many of my students are pre-pharmacy, so having a medical tie-in increases the students’ interest in the case. The case also forces the students to recall material previously learned (E/Z designations) while learning new concepts (such as lactam/lactim). I allow the students to form groups and work together outside of class. They submit their answers to the questions which count toward part of their grade on their first exam.

Susan Choi
Department of Chemistry
Camden County College
Blackwood, NJ

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