Ordinary ampholytes

In this category of ampholytes, the pKa of the acidic group, pKfidic, is higher than that of the basic group, pKbasic, and consequently the first group that loses its proton as the pH is increased is the basic group. Table 3.6 includes several examples of this type of ampholyte. We will consider, as a simple example, the ionisation of m-aminophenol (I), which has pKfidic = 9.8 and pKbasic = 4.4.

The steps of the ionisation on increasing pH are shown in the following equilibria:

NH+C6H4OH

NH2C6H4OH

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