Kinetic Study of the Hexacyanoferrate (III) Oxidation of Dihydroxyfumaric Acid in Acid Media

Abstract

The kinetics of the hexacyanoferrate (III) oxidation of dihydroxyfumaric acid to hexacyanoferrate (II) and diketosuccinic acid was looked into within the 0.04 to 5.3 M HCl acidity range under different temperatures, ionic strengths, and solvent permittivity conditions. The kinetic effect of alkali metal ions, transition metal impurities, and substrate concentrations have also been analyzed. The observed inhibition effect brought about by addition of the reaction product, hexacyanoferrate (II), is a sign of a complex mechanism. The rate constants remained essentially unchanged up to 1 M HCl, diminished between 1.0 and 3.0 M HCl, and rose above 3.0 M HCl. Depending on the medium acidity, three mechanisms can be put forward, which involve different kinetically active forms. At low acidity, the rate-determining step involves a radical cation and both the neutral and the anion substrate forms are equally reactive ( k 1 = k 2 = 2.18 +/- 0.05 M (-1) s (-1), k -1 = 0.2 +/- 0.03). When the medium acidity is boosted, the rate-determining step involves the neutral dihydroxyfumaric acid and two hexacyanoferrate (III) forms. In the intermediate region the rate constant diminished with rising [H (+)] ( k' 1 = 0.141 +/- 0.01 and k' 2 = 6.80 +/- 0.05). Specific catalytic effect by binding of alkali metal ions to oxidant has not been observed. In all instances it was assessed that the substrate decomposition is slow compared to the redox reaction.

Palladium(II)-catalyzed oxidation of l-tryptophan by hexacyanoferrate(III) in perchloric acid medium: a kinetic and mechanistic approach

“…The existence of higher protonated complexes is ruled out as they exist at relatively higher [H + ]. 42 Thus, a single protonated ferricyanide, H[Fe(CN) 6 ] 2− , may be the reactive species in the present investigation.…”

Exploratory Experiments on the Chemistry of the “Glyoxylate Scenario”: Formation of Ketosugars from Dihydroxyfumarate

“…Only rare cases involving glyoxylic acid (or its salts) as a partner in aldol reaction, especially in mixed-aqueous medium, had been documented . Moreover, for DHF, only two major reaction pathways in aqueous medium had been identified previously: (a) the decarboxylative conversion to glycolaldehyde , and (b) the oxidative transformation to dioxosuccinic acid, leading to the perception that DHF (and its salts) in water are “unstable”; in addition, DHF and its Na + , K + , and NH 4 + salts are sparingly soluble in water. Of these documented observations, the decarboxylative conversion of DHF to glycolaldehyde and the (in)­solubility of DHF (and its salts) in aqueous medium are expected to play a central role in the context of the “glyoxylate scenario”.…”

Base-Mediated Cascade Aldol Addition and Fragmentation Reactions of Dihydroxyfumaric Acid and Aromatic Aldehydes: Controlling Chemodivergence via Choice of Base, Solvent, and Substituents

“…The reactivity of DHF, a molecule that was reported by Fenton in the 1890s, , has been the subject of recent studies (Figure ). While it has been primarily reported as a reducing agent (oxidation to dioxosuccinic acid), DHF has also been shown to undergo reduction to tartaric acid. , Due to its inherent propensity toward oxidation, DHF has been used as an additive in various food and wine preparations as an antioxidant . DHF also undergoes CO 2 – group migration (benzilic acid type rearrangement) upon oxidation with O 2 and hydroxide to form di- and trisubstituted methoxide anions, which have been used to make ligand complexes and coordination polymers .…”