88466-19-7Relevant academic research and scientific papers
Mechanism of the Oxidation of Dopamine by the Hydroxyl Radical in Aqueous Solution
Richter, Helen W.,Waddell, Walter H.
, p. 5434 - 5440 (1983)
The hydroxyl radical (HO*) reacts with dopamine (4-(2-aminoethyl)-1,2-benzenediol) via one-electron oxidation producing o-semiquinone and o-semiquinone anion radicals, k = 5.9 * 109 M-1 s-1.Reaction of OH* with protonated dopamine (H+QH2) proceeds via addition to the aromatic ring, while reaction with deprotonated dopamine (H+QH-) proceeds via direct, one-electron oxidation.The isomeric hydroxycyclohexadienyl radicals formed via addition of HO* to H+QH2 yield three kinetically distinguishable groups (1- and 2-, or 3- and 6-, or 4- and 5-hydroxycyclohexadienyl radicals) with regard to rates of water elimination to produce semiquinone radicals; dehydration is "very fast" (addition of OH* ipso to an OH group), "fast" or "slow".The fast and slow reactions are acid and base catalyzed, with minimum rates at pH 4-5.Acid catalysis appears to be specific, while base catalysis is general.Spectra were determined for the initial products of HO* reaction with H+QH2 at pH 3.1 and 4.7.Deprotonation of the HO* adducts is the rate-controlling step in the base-catalyzed water loss at pH 2-, HO-, and PO43- were 1.7 * 102, 6.5 * 108, 11, and 11 M-1 s-1, respectively; for the last reaction, rate constants for H2O and HPO42- were 1.1 * 103 and 2.2 * 108 M-1 s-1, respectively.
Redox Reactions of Dopamine Transients in Aqueous Solution: a Pulse Radiolysis Study
Maity, Dilip K.,Mohan, Hari,Mittal, Jai P.
, p. 919 - 924 (2007/10/02)
On reaction of e-eq with protonated dopamine (D) a transient optical absorption band max = 355 nm (ε = 5100 dm3 mol-1 cm-1)> has been assigned to an e-eq adduct of the dopamine ring (D-radical anion) (the first site of attack of e-eq), which subsequently goes to the amine site to cleave the C-N bond.The bimolecular rate constant for the reaction of e-eq with protonated dopamine has been determined to be 2.5*108 dm3 mol-1 s-1.The transient optical absorption band (λmax = 355 nm, ε = 3760 dm3 mol-1 cm-1) formed on reaction of H atoms with protonated dopamine has been assigned to a H-adduct of dopamine.The bimolecular rate constant for the reaction has been determined to be 4.2*108 dm3 mol-1 s-1 from the build up kinetics of the 355 nm band.The transient H-adduct decays with the formation of ammonia.The isopropanol radical is unable to undergo a one electron transfer reaction with dopamine, whereas an equilibrium is established between the benzamide radical anion and dopamine from which the redox potential for the D/D-radical anion couple has been determined to be -1.91 V.The dopamine radical anion (D-radical anion) is a strong reducing agent and is able to reduce methyl violegen with a bimolecular rate constant of 3.3*1010 dm3 mol-1 s-1.Specific one electron oxidants are able to undergo one electron transfer reactions forming a dopamine semiquinone radical (DSQ-radical) ( λmax = 290 nm, ε = 7750 dm3 mol-1 cm-1).
