BL/CH 401 Lecture #3 - Acids, Bases, and Buffers

4. Ionization Rules 1:

How do you tell which group (carboxylic acid or amino) on Gly ionizes first?

It depends on the chemical nature of the group.

GENERAL RULES:

1. Alpha Carboxylic acids ionize at acidic pH and have pKs less than 6

So in titrating a fully protonated amino acid, carboxylic acids lose the proton first

2. Alpha Amino groups ionize at basic pH and have pKs greater than 8

So after acids lose their protons, amino groups lose their proton second.

©Wilbur H. Campbell, 1995, 1996; wcampbel@mtu.edu

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