Starter
1) Draw [Cu(EDTA)]2-
1) Draw the two optical isomers of [Co(H2O)2(NH2CH2CH2NH2)2]2+
edta
L.O.:
Describe the process of ligand substitution.
Describe examples of ligand substitution using [Cu(H2O)6]2+ and [Co(H2O)6]2+ with ammonia and chloride ions.
Common ligand substitution reactions
Reaction No.
Aqueous complex Complex with substituted ligands
1 [ Cu(H2O) 6]2+ (aq) Pale blue solution
[Cu(NH3) 4(H2O) 2]2+ (aq)Deep blue solution
2 [ Cu(H2O) 6]2+ (aq) Pale blue solution
[CuCl 4]2- (aq)Yellow solution
3 [ Co(H2O) 6]2+ (aq) Pink solution
[CoCl 4]2- (aq)Blue solution
Ligand substitution and equilibria
Looking at the table you have just drawn, describe and explain would happen to the position of the equilibrium if:
1.You increased the amount of HCl you added to no. 2
2.You added more water to no. 1.3.If the forward reaction in no. 2 was
exothermic and you heated the solution.4.EXTENSION: You added EDTA to number 3.
The Haem group in Haemoglobin (Hb)
Iron and the heme prosthetic group
How the haem group binds to the heamoglobin protein
The Haem group
• The iron (II) ion forms four bonds with the haem group, one with the O2 and another with the protein part of the Hb
• The coordinate bond with the O2 is a temporary bond and allows Hb to acts as a transporter molecule
• However, CO can bind instead of O2 and it does so irreversibly, rendering the haem molecule it is bound to unable to carry oxygen
Equilibrium constant, Kc
• For each of the three equilibriums in your table write out the expression for the equilibrium constant
Stability constant
• For equilibriums involving complexes we use the term stability constant instead (Kstab)
• A large Kstab means that the complex is very stable, and so suggests that the ion is very easily formed
• NB: We usually do not include water in the stability constant because usually it is such excess that its concentration effectively remains the same throughout.
Writing the units to Kstab
• Worked out in just the same way as in Kc
• Work out the units for each of the Kstab
expressions you have worked out