A green approach to Fenton chemistry: mono-hydroxylation of salicylic acid in aqueous medium by the electrogeneration of Fenton's reagent

TY - JOUR

T1 - A green approach to Fenton chemistry: mono-hydroxylation of salicylic acid in aqueous medium by the electrogeneration of Fenton's reagent

AU - Panchompoo, Janjira

AU - Aldous, Leigh

AU - Kabeshov, Mikhail

AU - Pilgrim, Ben S.

AU - Donohoe, Timothy J.

AU - Compton, Richard G.

PY - 2012

Y1 - 2012

N2 - First, the electrochemical characteristics of Fenton's reagent (Fe(III), Fe(II) and hydrogen peroxide), including its catalytic (EC′) behaviour were investigated. Second, the electrogeneration of hydrogen peroxide by a two-electron reduction of dissolved oxygen was conducted at a carbon electrode in a divided electrolysis cell and the concentration of hydrogen peroxide obtained was determined by the titration. The two approaches were then combined to give a one-pot, relatively green approach to aromatic hydroxylation reactions, with the electro-Fenton method allowing the iron to be used catalytically and the oxygen/water employed as the hydroxylation reagent by the in situ production of hydrogen peroxide. In particular, the preparative-scale hydroxylation of salicylic acid has been studied in an oxygen-saturated 0.1 M Na2SO4 pH 3.0 solution containing 5 mM Fe(II) and 5 mM salicylic acid at the controlled potential of −1.0 V vs. SCE. The study showed that after the attack of the hydroxyl radical produced in situ by the electro-Fenton process on salicylic acid, 2,3- and 2,5-dihydroxybenzoic acids were detected as primary monohydroxylated products with the highest yield of ca. 21.6 ± 2.5%.

AB - First, the electrochemical characteristics of Fenton's reagent (Fe(III), Fe(II) and hydrogen peroxide), including its catalytic (EC′) behaviour were investigated. Second, the electrogeneration of hydrogen peroxide by a two-electron reduction of dissolved oxygen was conducted at a carbon electrode in a divided electrolysis cell and the concentration of hydrogen peroxide obtained was determined by the titration. The two approaches were then combined to give a one-pot, relatively green approach to aromatic hydroxylation reactions, with the electro-Fenton method allowing the iron to be used catalytically and the oxygen/water employed as the hydroxylation reagent by the in situ production of hydrogen peroxide. In particular, the preparative-scale hydroxylation of salicylic acid has been studied in an oxygen-saturated 0.1 M Na2SO4 pH 3.0 solution containing 5 mM Fe(II) and 5 mM salicylic acid at the controlled potential of −1.0 V vs. SCE. The study showed that after the attack of the hydroxyl radical produced in situ by the electro-Fenton process on salicylic acid, 2,3- and 2,5-dihydroxybenzoic acids were detected as primary monohydroxylated products with the highest yield of ca. 21.6 ± 2.5%.

U2 - 10.1039/c2nj21007j

DO - 10.1039/c2nj21007j

M3 - Article

SN - 1144-0546

VL - 36

SP - 1265

EP - 1272

JO - NEW JOURNAL OF CHEMISTRY

JF - NEW JOURNAL OF CHEMISTRY

IS - 5

ER -