An organic acid is a carbon-based compound with acidic properties, while an organic base is a carbon-based compound with basic properties. Thus, an acid-base reaction in Organic Chemistry draws on the same rules, except that it deals only with carbon-based compounds. So instead of looking at acids such HCl, Organic Chemistry will examine organic acids such as CH3COOH. Other functional groups are also examined, which include but are not limited to alcohols (-OH), carboxyl groups (-COOH) and sulfonic acids (-OSO2H).
A typical acid is one that is a proton donor, while a base is usually a proton acceptor. Thus, by viewing it in this light, the acidity of certain compounds can be measured by the concentration of protons. This measurement is also known as the power of hydrogen, or pH:
pH = -log([H+])
However, since most organic acids are weak acids, then Ka and pKa are values that are also considered in acid-base calculations:
Ka = [H+][A-]/[HA]
While pKa = -log(Ka)
pH and pKa are also related in the following manner:
pH = pKa + log([A-]/[HA])
Thus, understanding the definition of an organic acid and base as well as the relationships between these two entities is crucial to understanding how to interpret these organic reactions no matter how complex.