Benniston L1 Flashcards
(18 cards)
When we look at inorganic mechanisms what are we interested in
- how the ligand attaches and detaches from a metal
- whether electrons move (oxidation/reduction)
What are the 3 broad types of reactions does octahedral complexes undergo
Ligand substitution
Electron transfer
Ligand activation
What is ligand substitution
One ligand is replaced by another, either associative or dissociative
What is electron transfer
Change in oxidation state of the metal
What is ligand activation
Activation of ligands after binding to the metal
What is a reaction mechanism
A mechanism describes all the pathways in which a reactant is converted to a product
What does a reaction mechanism explain
- how a reaction starts (activation)
- whether there is an intermediate and the structure of the intermediate
- how the product is formed/ how the intermediate goes to the product
What can using the rate law tell us about a reaction mechanism
1) number and type of each molecule participating in the formation of the transition state
2) the rate constant - how fast the reaction is
What is the problem with using the rate law to help determine reaction mechanisms
It does not give us enough information, it does not tell us if there are any intermediates, reversible steps or the energy barrier.
What conditions do we need to determine the rate law in probing mechanisms
Use pseudo first order conditions, where one reactant is used in a huge excess so it concentration doesn’t really change, this simplifies the rate law and helps us isolate the effect on one variable
What is the eyring equation and what is it used for
Temperature dependence of a reaction is measured because this can be related to the enthalpy of activation and the entropy of activation.
What is the eyring equation and what is it used for
Temperature dependence of a reaction is measured because this can be related to the enthalpy of activation and the entropy of activation.
Describe the eyring plot
A plot of ln(k/T) vs 1/T should be a straight line of slope –∆H‡/R
and intercept [ln kB/h + ∆S‡/R ]
What does the enthalpy of activation tell you
Tells you how strong the bonds are in the transition state
High enthalpy of activation - strong bonds more energy needed to break them -> slower reaction
Low enthalpy of activation - less energy needed to break-> faster reaction
What does the entropy of reaction tell you
Entropy of activation tells you whether the transition state is more ordered or more disordered than the reactants.
Positive S -> more disordered (dissociative)
Negative S -> more order (associative)
What is a multistep mechanism
Multistep mechanism is a reaction that doesn’t happen in a single jump, it happens in two or more elementary steps. Only one step is the rate determining step
Describe the effect of temperature in a multistep reaction
In multistep reactions different steps become the rate determining steps at different temperatures and you will get a curved eyring plot
