Etiqueta: kinetics

Using pseudophase models to determine antioxidant distributions in emulsions: why dynamic equilibrium matters

Publicada en por antiox@uvigo.es

Distributions of a homologous series of protocatechuic acid (PCA) derivatives of increasing lipophilicity were determined in stripped soybean oil-in-water emulsions and compared with their antioxidant (AO) efficiencies. The distribution was determined by employing a recently developed a kinetic method, based on the reaction between the hydrophobic 4-hexadecylbenzenediazonium ions (16-ArN2+) and the antioxidants [...]

Kinetic evidence for the formation of diazo ethers in the course of reactions between arenediazonium ions and antioxidants

Publicada en por antiox@uvigo.es

The reactions between arenediazonium ions, ArN2+, and phenolic antioxidants, AOs, are of interest because ArN2+ are involved in carcinogenic and mutagenic processes in contrast to phenolic AOs, that have biological activity and potential beneficial effects on health, and because an ArN2+ is currently being employed as a chemical probe to assess the distribution of AOs in lipid-based food emulsions [...]

kinetics and mechanism of the reaction between 3-methylbenzenediazonium ions and catechol

Publicada en por antiox@uvigo.es

We have investigated the kinetics and mechanism of the reaction between 3-methylbenzenediazonium, 3MBD, ions and catechol (1,2-dihydroxybenzene, [CAT]) in aqueous buffer solution under acidic conditions by employing spectrometric UV/VIS. The variation of the observed rate constant, kobs, with the acidity at a given [CAT] follows an upward curve [...]

A physicochemical study of the effects of acidity on the distribution and antioxidant efficiency of Trolox in olive-oil in water emulsions

Publicada en por antiox@uvigo.es

The efficiency of antioxidants to inhibit the oxidation of lipid-based emulsions depends on several factors including their nature and their concentration at the reaction site. Here, we have analyzed the effects of acidity and of surfactant concentration on the distribution and efficiency of the vitamin E analog Trolox (TR) in stripped olive oil-in-water emulsions stabilized with Tween 20 [...]

Interfacial kinetics in octane based emulsions. Effects of surfactant concentration on the reaction between 16-ArN2+ and octyl and lauryl gallates

Publicada en por antiox@uvigo.es

Here we have applied the formalism of the pseudophase kinetic model to analyze the reactivity of 4-hexadecylbenzenediazonium, 16-ArN2+, ions with the antioxidants octyl gallate (OG) and lauryl gallate (LG) in emulsions composed of octane, acidic water and hexaetyleneglycol monododecyl ether, C12E6 [...]

Temperature and emulsifier concentration effects on gallic acid distribution in a model food emulsion

Publicada en por antiox@uvigo.es

We determined the effects of emulsifier concentration and temperature on the distribution of gallic acid (GA) in a food-grade emulsion composed of 1:9 vol:vol stripped corn oil, acidic water and Tween 20. The distribution of GA can be defined by the partition constant between the aqueous and the interfacial regions, View the MathML source, which was determined by using a kinetic method and the pseudophase kinetic model [...]

Reactivity of 3-Methylbenzenediazonium ions with Gallic Acid. Kinetics and Mechanism of the Reaction

Publicada en por antiox@uvigo.es

We investigated the kinetics and mechanism of the reaction between the 3-methylbenzenediazonium ions (3MBD), and gallic acids (=3,4,5-trihydroxybenzoic acid; GA) in aqueous buffer solution under acidic conditions by employing spectrometric, electrochemical, and chromatographic techniques and computational methods [...]

Dediazoniation of 1-naphthalenediazonium tetrafluoroborate in aqueous acid and in micellar solutions

Publicada en por antiox@uvigo.es

We have measured the rates and product yields of dediazoniation of 1-naphthalenediazonium (1ND) tetrafluoroborate in the presence and absence of sodium dodecyl sulfate (SDS) micellar aggregates by employing a combination of UV–vis spectroscopy and high-performance liquid chromatography [...]

Micellar effects on the reaction between an arenediazonium ion and the antioxidants gallic acid and octyl gallate

Publicada en por antiox@uvigo.es

The effect of sodium dodecyl sulfate (SDS) micelles on the reaction between the 3-methylbenzenediazonium (3MBD) ion and either the hydrophilic antioxidant gallic acid (GA) or the hydrophobic analogue octyl gallate (OG) have been investigated as a function of pH [...]

Kinetic and Mechanism of the reaction between 4-hexadecylbenzenediazonium ions and vitamin C in emulsions: Further evidence of the formation of diazo ether intermediates in the course of the reaction

Publicada en por antiox@uvigo.es

The kinetics and mechanism of the reaction between hydrophobic 4-hexadecylarenediazonium ions, 16-ArNmath image and vitamin C, VC, in a model emulsion prepared by mixing octane, acidic (HCl) water and the non-ionic surfactant hexaethyleneglycol monododecyl ether, C12E6, were investigated [...]