![[Halogenation of Propanone - Mechanism A]](../images/four1a.gif)
HALOGENATION OF PROPANONE
Review
| Overall Reaction | Pk + I2 → PI + H+ + I- |
| Proposed Mechanism | |
If the reaction
Pk + I2 → PI + H+ + I-was elementary, the rate law could be written as:
-d[I2]/dt = +k[Pk][I2]i.e. 1st Order with respect to both Pk and I2.
However this is inconsistent with the known fact that the reaction is 0th Order with respect to halogen, and so it can be stated that the overall reaction is not elementary.
Obtaining the 0th Order Rate Coefficient
Since the reaction is known to be 0th Order with respect to halogen, the following can be written:
Rate = -d[I2]/dt = k0
Therefore, the 0th Order rate coefficient (and hence the rate) can be obtained from the gradient of a plot of