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The Iridium Cyle
click below to see the cyle build up step by step
| The promotor must be intervening to speed up the slower steps of the cycle. |
| The addition of iodomethane to iriduium (step 1) is about 150 times faster than addition to rhodium. |
|
Question a) Watch the cycle carefully. Is the first step still rate determining? b) The observed overall rate law is
Rate = [catalyst] x [CO]
c) Sketch the energy profile you would expect for the first two steps of the iridium cycle.
|
a) No the first step is now the fastest
b) Step 2 is slower than step 1, and step 2 involves both the catalyst, and
incoming CO. Since iodide is eliminated then it is reasonable that the rate
is slower if the concentration of iodine in solution is higher, and so the
iodide appears on the bottom line of the rate equation.
c)
The activation energy of the first step is lower than the activation energy of the second step, and so the first step is faster
