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Flashcards in Andy Burrows Deck (11):

Why is the 3+ oxidation state less favoured as you go from left to right?

Increase in nuclear charge so more difficult to remove the electrons


As oxygen binds to one iron the affinity of the remaining iron centres for oxygen increases. Why?

As the iron moves into the haem ring, it pulls on the protein; the resulting conformational changes in the protein chains leads to communication between the haem groups


What is the mechanism of action of cis-platin?

First the cis-platinum is hydrolysed in the cell
Labile water ligands replaced by nitrogen atoms from TWO of the DNA BASE PAIRS
The majority of Pt bridges two neighbouring guanine bases on the same strand of the double helix
Guanine tings then tilt from their normal position distrusting the helix and preventing it replicating


What are the entropic contributions to the chelate effect?

Increase in number of molecules from left to right so increase in disorder
As one end of the en ligand is coordinated less rearrangement is needed for the other end to coordinate as opposed to another ligand altogether


What is a hard acid/base?

High charge density
Non polarisable


What is a soft acid/base?

Low charge density


What mechanism do square planar complexes usually undergo?



What is the evidence for associative mechanisms in square planar complexes

Similar rate constants for displacement of Cl- by H2O in a variety of Pt complexes
Most reactions occur with stereoretention
Reactions display large negative entropy of activation - loss of molecular freedom approaching the transition state
If the pressure is increased substitution is accelerated and a large negative volume of activation is observed


What is he influence of spectator ligands on substitution?

Increasing the steric bulk of the spectator ligands slows substitution especially when the bulky ligand is cis to the leaving group X


Through what mechanism are octahedral substitutions most likely to occur?



What evidence is there for dissociative mechanisms for octahedral complexes?

Rates are typically unaffected by entering groups
Rates depend on the nature of the leaving groups
Rates increased by increasing the steric bulk of the spectator ligands
Increasing the pressure slows the reaction