Oxidation of caffeine by phosphate radical anion in aqueous solution under anoxic conditions

Kumar, Mukesh; Adinarayana, M.

doi:10.1007/bf02709288

Cited by 15 publications

(13 citation statements)

References 13 publications

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“…In‐situ generated radicals such as persulfate (SO 4 .− ),16 hydroxyl (OH . )16 and phosphate (PO 4 2.− )17 radicals were employed to examine the oxidation mechanism in aqueous solutions. It was verified by HPLC that 1,3,7‐trimethyluric acid was the main product formed between CAF and SO 4 .− , OH .…”

Section: Introductionmentioning

confidence: 99%

Electrochemically Controlled One‐Electron Oxidation Coupled to Consecutive Hydrogen Atom Transfer of Caffeine

Chan

Ganguly

et al. 2014

ChemElectroChem

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Caffeine (CAF) undergoes a one‐electron oxidation in acetonitrile to form a cation radical, with variable scan rate CV experiments indicating that the lifetime of the cation radical improves as the trace water content of the solvent is decreased. Electrochemical oxidation (and chemical oxidation with NOSbF6) of CAF in CH3CN leads to the generation of the protonated CAF cation as the long‐term product in high yield, whose structure is confirmed by single‐crystal X‐ray crystallography and NMR spectroscopy. The protonated cation is able to be electrochemically reduced back to CAF under electrolysis conditions. The formation of the protonated cation involves the initial one‐electron oxidation of CAF to form the cation radical, which undergoes a hydrogen atom abstraction reaction. Digital simulations of the CV data show that the rate and equilibrium constants for the hydrogen atom abstraction step are kf=1.0×102 L mol−1 s−1 and Keq=1.0×102.

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Section: Introductionmentioning

confidence: 99%

Electrochemically Controlled One‐Electron Oxidation Coupled to Consecutive Hydrogen Atom Transfer of Caffeine

Chan

Ganguly

et al. 2014

ChemElectroChem

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“…The oxidation of uracil by t-BuO  radicals has been carried out by irradiating the reaction mixture containing known concentrations of uracil and tBuOOH in the presence of sufficient amount of tBuOH to scavenge the  OH radicals completely 34 .The reaction was followed by measuring the absorbance of uracil at 258 nm ( max of uracil) with time. The initial rates and quantum yields of oxidation of uracil by t-BuO  are presented in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…The quartz cuvette containing the sample was irradiated and the irradiations were interrupted at definite intervals of time and the absorbance was noted. The light intensity corresponding to the irradiating wavelength (254nm) was measured using peroxydisulphate chemical actinometry 34 .…”

Section: Methodsmentioning

confidence: 99%

Untitled

2015

IJPSR

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ABSTRACT:The rates of oxidation of uracil and chlorogenic acid (CGA) by tertbutoxyl radicals have been studied by measuring the absorbance of uracil at 258 nm and CGA at 328 nm spectrophotometrically. tert-butoxyl radicals are generated by the photolysis of tert-butyl hydroperoxide in presence of tert-butyl alcohol to scavenge  OH radicals. The rates and the quantum yields () of oxidation of CGA by t-BuO  radicals have been determined in the absence and presence of varying concentrations of uracil. An increase in the concentration of uracil has been found to decrease the rate of oxidation of CGA suggesting that uracil and CGA compete for t-BuO  radicals. Using competitive kinetic studies, the rate constant for the reaction of t-BuO  radical with uracil has been found to be 4.43 10 8 dm 3 mol -1 s -1 . The quantum yields ( expt ) have been calculated from the experimentally determined rates of oxidation of CGA under different experimental conditions. Assuming that CGA acts as a scavenger of t-BuO  radicals only, the quantum yields ( cal ) have been theoretically calculated.  expt and  cal values suggest that CGA not only protects uracil from t-BuO  radicals but also repairs uracil radicals formed by the reaction of uracil with t-BuO  radicals.

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“…The quartz cuvette containing the sample was irradiated, the irradiations were interrupted at specific intervals of time, and the absorbance was noted. The light intensity equivalent to the irradiating wavelength (254 nm) was measured using peroxydisulphate chemical actinometry . On photolysis, t ‐BuOOH was triggered at 254 nm to make OH and t ‐BuO radicals through the homolytic cleavage of –O–O– bond.…”

Section: Methodsmentioning

confidence: 99%

Photo‐oxidation of some flavonoids with photochemically generatedt‐BuO^•radicals in at‐BuOH water system using a kinetic approach

Mallepu

Potlapally

2018

J Chinese Chemical Soc

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As a dietary component, flavonoids are thought to have a variety of pharmacological and health‐promoting properties in both in vivo and in vitro systems. This variety is attributed to their high antioxidant capacity, which in turn is associated with their free radical scavenging properties. In order to understand the mechanism of t‐BuO• radical scavenging properties of some flavonoids, viz, quercetin (QU), apigenin (AP), daidzein (DA), genistein (GE), myricetin (MY), and kaempferol (KA), a kinetic study of photo‐oxidation of these flavonoids with photochemically generated t‐BuO• radicals in a t‐BuOH water (2:1 v/v) system was carried out. The oxidation of flavonoids by t‐BuO• radicals was performed spectrophotometrically by measuring the absorbance of quercetin (375 nm), apigenin (340 nm), daidzein (250 nm), genistein (263 nm), myricetin (255 nm), and kaempferol (375 nm) at their respective λmax. The initial rates of oxidation of flavonoids increased with [flavonoid], [t‐BuOOH], and light intensity. The quantum yields (φ) were considered from the initial rate of oxidation of flavonoids by t‐BuO• radicals and measured light intensity at 254 nm. The order on [flavonoid] and [t‐BuOOH] was found to be fractional, whereas the order on light intensity was found to be one. The products of the oxidation of flavonoids by t‐BuO• radicals were identified using LC–MS and FTIR analysis.

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Oxidation of caffeine by phosphate radical anion in aqueous solution under anoxic conditions

Cited by 15 publications

References 13 publications

Electrochemically Controlled One‐Electron Oxidation Coupled to Consecutive Hydrogen Atom Transfer of Caffeine

Electrochemically Controlled One‐Electron Oxidation Coupled to Consecutive Hydrogen Atom Transfer of Caffeine

Untitled

Photo‐oxidation of some flavonoids with photochemically generatedt‐BuO^•radicals in at‐BuOH water system using a kinetic approach

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Oxidation of caffeine by phosphate radical anion in aqueous solution under anoxic conditions

Cited by 15 publications

References 13 publications

Electrochemically Controlled One‐Electron Oxidation Coupled to Consecutive Hydrogen Atom Transfer of Caffeine

Electrochemically Controlled One‐Electron Oxidation Coupled to Consecutive Hydrogen Atom Transfer of Caffeine

Untitled

Photo‐oxidation of some flavonoids with photochemically generatedt‐BuO•radicals in at‐BuOH water system using a kinetic approach

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Photo‐oxidation of some flavonoids with photochemically generatedt‐BuO^•radicals in at‐BuOH water system using a kinetic approach