Page 64 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102

Table 1: Typical functional groups involved in chelation

Acidic or Anionic Groups Uncharged Groups

Carboxylic acid OO Amines NH2 , H ,
N
C OH or C O

Oximes NOH or NO Carbonyl N
Hydroxyles O

Phenols C

Sulfonic acids R OH or R O Thiocarbonyl S
Mercaptyl C

OH O Nitroso NO

or O Cyclic amine N
SO
O O
S OH

O or

R SH or R S

Stability of Complexes

The stability of a species is a measure of the extent to which this
species will be formed from other species under certain conditions,
provided that the system is allowed to reach equilibrium. Consider a
metal ion M in solution together with a monodentate ligand L, then the
system may be described by the following stepwise equilibria:

M+L ML; K1 = [ML] / [M] [L]
ML + L
ML(n-1) + L ML2; K2 = [ML2] / [M] [L]
MLn; Kn = [MLn] / [M(n-1)] [L]

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