Dakin oxidation

The Dakin reaction or Dakin oxidation is a name reaction in organic chemistry, it was introduced in 1909 for the first time by Henry Drysdale Dakin and is used to divalent phenols from 2 - to synthesize or 4 -hydroxybenzaldehyde. Instead of the substituted benzaldehyde and hydroxy sustituierte aryl ketones can be used as starting material.

The hydroxy group in the starting material can also be replaced by other substituents, with a M effect on the ring, such as an amino group. In addition, this group can be either in the ortho- and para -position to the carbonyl group. The Dakin reaction is a special case of a Baeyer -Villiger oxidation.

Mechanism

The reaction proceeds as described above starting with each functional group with M effect, but here the mechanism is to be shown exemplarily with only one hydroxyl group. In addition, the moiety can be either in the ortho and in the para-position, but this is only an example for demonstrating the para position in the mechanism.

First, the hydroxy group of the aryl ketone (R = Organylgruppe ) or the aryl aldehyde (R = H) in one form of the phenolate 2 is deprotonated. Under the action of hydrogen peroxide in an alkaline medium, the hydroperoxide 3, which rearranges to the quinoid epoxide 4 forms. Under rearomatization the ester produced 5 The alkaline hydrolysis of 5 supplies via the intermediate 6 is a carboxylic acid and 1,4- diphenolate 7 The stepwise protonation of 7 finally provides hydroquinone ( 9).