HALOGENATION OF PROPANONE

Review

Overall Reaction	Pk + I2 → PI + H+ + I-
Proposed Mechanism
Overall Rate of Consumption of Iodine	-d[I2]/dt = + k2[Pe][I2]

The Steady State Approximation

In the introduction to this chapter the following facts were given about the system:

• The halogen (I₂) is capable of reacting extremely rapidly with the enol form of propanone (P_e) to produce iodopropanone (PI).
• The enol form of propanone is present in ordinary propanone in very small proportion in equilibrium with a large proportion of the keto form (P_k).
• In the presence of halogen the equilibrium between the enol and keto forms of propanone is disturbed by the rapid removal of the enol form.

Therefore, if the Steady State Approximation is to be used, it should be applied to

d[H⁺]/dt

d[I^-]/dt

d[I₂]/dt

d[P_e]/dt

d[PI]/dt

d[P_k]/dt