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pKa values in the undergraduate curriculum: introducing pKa values measured in DMSO to illustrate solvent effects

Authors
  • Heller, Stephen T.1
  • Silverstein, Todd P.2
  • 1 Loyola Marymount University, Los Angeles, CA, 90045, USA , Los Angeles (United States)
  • 2 Willamette University, Salem, OR, 97301, USA , Salem (United States)
Type
Published Article
Journal
ChemTexts
Publisher
Springer International Publishing
Publication Date
Apr 23, 2020
Volume
6
Issue
2
Identifiers
DOI: 10.1007/s40828-020-00112-z
Source
Springer Nature
Keywords
License
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Abstract

AbstractThe concepts of acidity and pKa values often occupy a privileged place in the undergraduate organic chemistry curriculum. However, by neglecting the relationship between solvent and acidity, many students come to understand acidity as a fixed property of a molecule, invariant regardless of reaction conditions. Moreover, the sole use of pKa values measured in water leads to serious analytical faults in several important areas of the introductory organic curriculum. In this paper, we consider the (mis)uses of aqueous pKa values in the organic curriculum and their pedagogical effects, argue for the adoption of pKa values measured in an organic solvent (DMSO) in organic textbooks and reference materials, and explore the thermodynamic origin of the effect of solvent on acidity. Suggestions for class discussions and activities are provided.Graphic abstract

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