Concept explainers
Interpretation:
p-Nitrophenol and 2,6-dimethyl-4-nitrophenol both have a pKa of 7.15 but 3,5-dimethyl-4-nitrophenol has pKa of 8.25. Why 3,5-dimethyl-4-nitrophenol is much less acidic is to be explained.
Concept introduction:
Resonance delocalization occurs only when the molecule is planar facilitating the overlapping of the orbitals. If the substituent groups present prevent co-planarity of the molecule then resonance is not possible.
pKa = -log Ka, where Ka is the dissociation constant of the acid. Thus a stronger acid has a low pKa value.
To explain:
Why 3,5-dimethyl-4-nitrophenol is much less acidic with pKa of 8.25 when compared to p-nitrophenol and 2,6-dimethyl-4-nitrophenol both of which have a pKa of 7.15.
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Chapter 17 Solutions
Organic Chemistry
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- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning