Partitioning of aryl radicals in micellar systems

Determining the association constants of radicals to biomimetic systems is not a simple task because of the inherent experimental difficulties associated to their “in‐situ” generation together with their high chemical instability, requiring the use of radical trapping agents in combination with, for example, magnetic (eg, EPR) and/or time‐resolved techniques (eg, frequency comb spectroscopy) to indentify and quantify them. Here, we have exploited the unique electrochemical properties of arenediazonium ions, ArN2+, to estimate the association constant of the electrochemically generated aryl radicals derived from benzenediazonium ions, BD, with sodium dodecyl sulfate (SDS) micelles [...]

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

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

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 [...]

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

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 [...]

Effects of acidity, temperature and emulsifier concentration on the distribution of caffeic acid in stripped corn and olive oil in water emulsions

We evaluated the effects of oil type, oil to water ratio, emulsifier concentration, acidity, and temperature on the distribution of caffeic acid, CA, in emulsions composed of stripped olive and corn oils, acidic water, and Tween 20. CA mainly distributes between the water and interfacial regions because it is sparingly soluble in oils, as demonstrated by auxiliary partitioning experiments in the absence of an emulsifier [...]

Maxima in antioxidant distributions and efficiencies with increasing hydrophobicity of gallic acid and its alkyl esters. The pseudophase model interpretation of the “cutoff effect”

Antioxidant (AO) efficiencies are reported to go through maxima with increasing chain length (hydrophobicity) in emulsions. The so-called “cutoff” after the maxima, indicating a decrease in efficiency, remains unexplained. This paper shows, for gallic acid (GA) and propyl, octyl, and lauryl gallates (PG, OG, and LG, respectively) [...]

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

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

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

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

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 [...]