pKa Prediction for Organic Acids and Bases

1. Front Matter

   Pages i-x

   PDF

2. Introduction

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 1-11

3. Molecular Factors that Modify pK a Values

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 12-20

4. Methods of pK a Prediction

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 21-26

5. Prediction of pK a Values of Substituted Aliphatic Acids and Bases

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 27-43

6. Prediction of pK a Values for Phenols, Aromatic Carboxylic Acids and Aromatic Amines

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 44-52

7. Further Applications of Hammett and Taft Equations

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 53-65

8. Some More Difficult Cases

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 66-81

9. Extension of the Hammett and Taft Equations

   • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

   Pages 82-95

10. Examples where Prediction Presents Difficulties

    • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

    Pages 96-103

11. Recapitulation of the Main pK a Prediction Methods

    • D. D. Perrin, Boyd Dempsey, E. P. Serjeant

    Pages 104-108

12. Back Matter

    Pages 109-146

    PDF

Many chemists and biochemists require to know the ionization constants of organic acids and bases. This is evident from the Science Citation Index which lists The Determination of Ionization Constants by A. Albert and E. P. Serjeant (1971) as one of the most widely quoted books in the chemical literature. Although, ultimately, there is no satisfactory alternative to experimental measurement, it is not always convenient or practicable to make the necessary measure­ ments and calculations. Moreover, the massive pK. compilations currently available provide values for only a small fraction of known or possible acids or bases. For example, the compilations listed in Section 1. 3 give pK. data for some 6 000--8 000 acids, whereas if the conservative estimate is made that there are one hundred different substituent groups available to substitute in the benzene ring of benzoic acid, approximately five million tri-substituted benzoic acids are theoretically possible. Thus we have long felt that it is useful to consider methods by which a pK. value might be predicted as an interim value to within several tenths of a pH unit using arguments based on linear free energy relationships, by analogy, by extrapolation, by interpolation from existing data, or in some other way. This degree of precision may be adequate for many purposes such as the recording of spectra of pure species (as anion, neutral molecule or cation), for selection of conditions favourable to solvent extraction, and for the interpretation of pH-profiles for organic reactions.

• amines
• aromatic
• carboxylic acid
• energy
• experiment
• extraction
• molecule
• phenol
• phenols
• reactions
• spectra

• John Curtin School of Medical Research, Australian National University, Canberra, Australia

  D. D. Perrin

• Faculty of Military Studies, University of New South Wales, Royal Military College, Duntroon, Australia

  Boyd Dempsey, E. P. Serjeant

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