Essays on Acid-Base Reactivity

Acid-base, or H+ transfer, reactions are crucial to organic chemistry for both practical and theoretical reasons.

At a simple, practical level: many reaction rates can be influenced by adding acids and bases. An acid can make a substrate into a better electron acceptor (more electrophilic), while a base can make a substrate into a better electron donor (more nucleophilic). Therefore, acids and bases are used to promote, and even catalyze, chemical reactions.

Equally important, H+ transfer changes a molecule's ionization state. Organic ions are often more water-soluble than their neutral counterparts, so acid-base chemistry may offer a way to separate organic compounds (the ions dissolve in any water that is present and leave the neutrals behind).

Water solubility also determines how a substance will migrate through our bodies and penetrate our cells. Water solubility also determines how a compound moves through the natural environment. Therefore, the acid-base reactivity of organic molecules plays an important role in medicinal and environmental chemistry.

Finally, the theory of acid-base reactivity guides our thinking about most other kinds of reactivity. Most organic reactions involve charge transfer and bond breaking and/or bond making. Acid-base reactions are the simplest kind of reaction of this type. Therefore, chemists have expended considerable effort in trying to understand what structural factors make a molecule a strong acid or base.

  1. Predict a molecule's ionization state
  2. Identify a molecule's most acidic proton
  3. Identify a molecule's most basic N or O
  4. Substituent field-inductive effects


pKa tables

  1. Bordwell's values (DMSO) - not water!
  2. Organic acids (H2O) - "Organic Chemistry" by Reusch, MSU
  3. Inorganic & organic acids (H2O/DMSO) - Evans, Harvard (PDF)
  4. Inorganic & organic acids (H2O) - Jencks-Westheimer (PDF)