Unit 2 Flashcards
How could you determine the resting state of a catalyst?
Resting state is the (metal-containing) species of highest concentration and
Carry out in situ spectroscopy i.e IR / UV and then use beer-lambert law to determine species with highest concentration
How could you determine the turnover limiting step in a catalytic cycle?
The turnover limiting step is the slowest step in a catalytic cycle which determines overall rate of catalytic cycle
Utilise the kinetic isotope effect.
-For each step in the cycle introduce substrates with selectively enriched ²D ¹³C for example and then measure the rate.
-The step which the rate changes significantly will be the turnover limiting step.
What is hydrosilylation?
Addition of H-SiR3 across an unsaturated double/triple bond
What effect does bulky ligands in hydrosilylation have on the double bonds?
They suppress the rate of reaction
What happens if the ligand is too bulky in hydrosilylation?
Can cause dimerisation espically with copper
How to stop unwanted side products in hydrocynation?
Change angle of the structure. 113° is best angle for reaction. Stops unwanted side products
Draw the mechanism of transfer hydrogenation and comment on all of the steps
1) beta hydride elimination
2) Migratory insertion
3) sigma bond metathesis
4) beta hydride elimination
What is an outer-sphere mechanism?
A mechanism where there is no interaction with the metal
What is tandem catalysis
Two or more metals taking part in two or more different cycles to produce a product
What is shvo’s catalyst a good example of
Remote group participation. in the case of shvo’s catalyst it is the carbonyl group
Dynamic kinetic resolution (DKR)
Shifts equilibrium between Ss and Sr towards Sr. This then favours product
What is a requirement of DKR?
That going from starting material to product is a irreversible reaction
How large should the Kr/Ks ratio be
large as possible (>20)
For DKR which rate constants should be equal to each other
Kinv = Kr
Examples of Lewis acids
AlCl3, SnCl2, ZnCl2
