scholarly journals An Insight into the Reactivity of the Electrogenerated Radical Cation of Caffeine

Electrochem ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 44-55
Author(s):  
Marta Feroci ◽  
Martina Bortolami ◽  
Isabella Chiarotto ◽  
Paola Di Matteo ◽  
Leonardo Mattiello ◽  
...  
Keyword(s):  
Current Efficiency ◽  
Radical Cation ◽  
Anodic Oxidation ◽  
Degradation Products ◽  
Oxidation Products ◽  
Coupling Reactions ◽  
Pt Electrode ◽  
Controlled Potential ◽  
Chromatographic Peaks ◽  
Insight Into

Controlled potential electrolyses of caffeine (CAF) were carried out at a Pt electrode in undried acetonitrile (ACN) and ACN-H2O and the products of the anodic oxidation were analyzed by HPLC-PDA-ESI-MS/MS. A higher current efficiency occurred in ACN-H2O, but an analogous chromatographic outline was found in both media, evidencing a reactive pathway of the electrogenerated radical cation CAF•+ with water, added or in trace, as nucleophile. No dimeric forms were evidenced, excluding any coupling reactions. Neither was 1,3,7-trimethyluric acid found, reported in the literature as the main oxidative route for CAF in water. Four main chromatographic peaks were evidenced, assigned to four proposed structures on the base of chromatographic and spectral data: a 4,5-diol derivative and an oxazolidin-2-one derivative were assigned as principal oxidation products, supporting a mechanism proposed in a previous work for the primary anodic oxidation of the methylxanthines olefinic C4 = C5 bond. Two highly polar degradation products were also tentatively assigned, that seemed generating along two different pathways, one opening the imidazolic moiety and another one opening the purinic one.

scholarly journals Occurrence and distribution of ladderane oxidation products in different oceanic regimes

2012 ◽  
Vol 9 (7) ◽  
pp. 2407-2418 ◽  
Author(s):  
D. Rush ◽  
E. C. Hopmans ◽  
S. G. Wakeham ◽  
S. Schouten ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Fatty Acids ◽  
Water Column ◽  
Arabian Sea ◽  
Degradation Products ◽  
Oxidation Products ◽  
Short Chain ◽  
Sediment Surface ◽  
Ammonium Oxidation ◽  
Anammox Activity ◽  
Sediment Matrix

Abstract. Ladderane fatty acids are commonly used as biomarkers for bacteria involved in anaerobic ammonium oxidation (anammox). These lipids have been experimentally shown to undergo aerobic microbial degradation to form short chain ladderane fatty acids. However, nothing is known of the production or the distribution of these oxic biodegradation products in the natural environment. In this study, we analysed marine water column particulate matter and sediment from three different oceanic regimes for the presence of ladderane oxidation products (C14 ladderane fatty acids) and of original ladderane fatty acids (C18 and C20 ladderane fatty acids). We found that ladderane oxidation products, i.e. C14 ladderane fatty acids, are already produced within the water column of the Arabian Sea oxygen minimum zone (OMZ) and thus only low amounts of oxygen (< 3 μM) are needed for the β-oxidation of original ladderane fatty acids to proceed. However, no short chain ladderane fatty acids were detected in the Cariaco Basin water column, where oxygen concentrations were below detection limit, suggesting that the β-oxidation pathway is inhibited by the absence of molecular oxygen, or that the microbes performing the degradation are not proliferating under these conditions. Comparison of distributions of ladderane fatty acids indicates that short chain ladderane fatty acids are mostly produced in the water column and at the sediment surface, before being preserved deeper in the sediments. Short chain ladderane fatty acids were abundant in Arabian Sea and Peru Margin sediments (ODP Leg 201), often in higher concentrations than the original ladderane fatty acids. In a sediment core taken from within the Arabian Sea OMZ, short chain ladderanes made up more than 90% of the total ladderanes at depths greater than 5 cm below sea floor. We also found short chain ladderanes in higher concentrations in hydrolysed sediment residues compared to those freely occurring in lipid extracts, suggesting that they had become bound to the sediment matrix. Furthermore, these matrix-bound short chain ladderanes were found at greater sediment depths than short chain ladderanes in the lipid extract, suggesting that binding to the sediment matrix aids the preservation of these lipids. Though sedimentary degradation of short chain ladderane fatty acids did occur, it appeared to be at a slower rate than that of the original ladderane fatty acids, and short chain ladderane fatty acids were found in sediments from the Late Pleistocene (~ 100 kyr). Together these results suggest that the oxic degradation products of ladderane fatty acids may be suitable biomarkers for past anammox activity in OMZs.

scholarly journals Arenium cation or radical cation? An insight into the cyclodehydrogenation reaction of 2-substituted binaphthyls mediated by Lewis acids

RSC Advances ◽  
2020 ◽  
Vol 10 (37) ◽  
pp. 21974-21985
Author(s):  
Patricia Camargo Solórzano ◽  
María T. Baumgartner ◽  
Marcelo Puiatti ◽  
Liliana B. Jimenez
Keyword(s):  
Radical Cation ◽  
Lewis Acid ◽  
Reaction Mechanisms ◽  
Lewis Acids ◽  
Acid Synthesis ◽  
Theoretical Studies ◽  
Insight Into

Cyclodehydrogenation reactions of 2-substituted binaphthyls induced by a Lewis acid. Synthesis and theoretical studies of the reaction mechanisms.

scholarly journals Isolation and Structure Determination of Echinochrome A Oxidative Degradation Products

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4778
Author(s):  
Natalia P. Mishchenko ◽  
Elena A. Vasileva ◽  
Andrey V. Gerasimenko ◽  
Valeriya P. Grigorchuk ◽  
Pavel S. Dmitrenok ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Degradation Products ◽  
Lethal Dose ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Ionization Mass ◽  
Echinochrome A ◽  
Esi Ms

Echinochrome A (Ech A, 1) is one of the main pigments of several sea urchin species and is registered in the Russian pharmacopeia as an active drug substance (Histochrome®), used in the fields of cardiology and ophthalmology. In this study, Ech A degradation products formed during oxidation by O2 in air-equilibrated aqueous solutions were identified, isolated, and structurally characterized. An HPLC method coupled with diode-array detection (DAD) and mass spectrometry (MS) was developed and validated to monitor the Ech A degradation process and identify the appearing compounds. Five primary oxidation products were detected and their structures were proposed on the basis of high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as 7-ethyl-2,2,3,3,5,7,8-heptahydroxy-2,3-dihydro-1,4-naphthoquinone (2), 6-ethyl-5,7,8-trihydroxy-1,2,3,4-tetrahydronaphthalene-1,2,3,4-tetraone (3), 2,3-epoxy-7-ethyl-2,3-dihydro-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (4), 2,3,4,5,7-pentahydroxy-6-ethylinden-1-one (5), and 2,2,4,5,7-pentahydroxy-6-ethylindane-1,3-dione (6). Three novel oxidation products were isolated, and NMR and HR-ESI-MS methods were used to establish their structures as 4-ethyl-3,5,6-trihydroxy-2-oxalobenzoic acid (7), 4-ethyl-2-formyl-3,5,6-trihydroxybenzoic acid (8), and 4-ethyl-2,3,5-trihydroxybenzoic acid (9). The known compound 3-ethyl-2,5-dihydroxy-1,4-benzoquinone (10) was isolated along with products 7–9. Compound 7 turned out to be unstable; its anhydro derivative 11 was obtained in two crystal forms, the structure of which was elucidated using X-ray crystallography as 7-ethyl-5,6-dihydroxy-2,3-dioxo-2,3-dihydrobenzofuran-4-carboxylic acid and named echinolactone. The chemical mechanism of Ech A oxidative degradation is proposed. The in silico toxicity of Ech A and its degradation products 2 and 7–10 were predicted using the ProTox-II webserver. The predicted median lethal dose (LD50) value for product 2 was 221 mg/kg, and, for products 7–10, it appeared to be much lower (≥2000 mg/kg). For Ech A, the predicted toxicity and mutagenicity differed from our experimental data.

Oxidation products of α- and β-amyrins: potential tracers of abiotic degradation of vascular-plant organic matter in aquatic environments

2016 ◽  
Vol 13 (4) ◽  
pp. 732 ◽  
Author(s):  
M.-A. Galeron ◽  
F. Vaultier ◽  
J.-F. Rontani
Keyword(s):  
Organic Matter ◽  
Degradation Products ◽  
Vascular Plant ◽  
Oxidation Products ◽  
Aquatic Environments ◽  
Rhône River ◽  
Abiotic Degradation ◽  
Suspended Particulate ◽  
Rhone River

Environmental contextHow can we know what happens to organic matter in aquatic environments? Although several compounds exist that can be used to trace the origin and state of organic matter, not many are sufficiently stable and specific to trace degradation processes, but α- and β-amyrins can fulfil that role. Such knowledge will help us better understand and better quantify carbon fluxes in riverine and marine environments. AbstractIn order to fulfil the current need for stable and specific tracers to monitor vascular-plant organic matter degradation in aquatic environments, α-amyrin (urs-12-en-3β-ol) and β-amyrin (olean-12-en-3β-ol) were oxidised in vitro and their abiotic degradation products quantified in environmental samples from the Rhône River in France. Although they appear inert to photooxidation, they are clearly affected by autoxidation and the tracer potential of the resulting products was confirmed. Autoxidation of α- and β-amyrins produces urs or olean-12-en-3-one, 3β-hydroxy-urs or olean-12-en-11-one, urs or olean-12-en-3β,11α-diol and urs or olean-12-en-3,11-dione. 3β-Hydroxy-urs-12-en-11-one and 3β-hydroxy-olean-12-en-11-one, the main oxidation products detected, were selected as autoxidation tracers. These compounds, specific to autoxidation, were detected in dry leaves of Smilax aspera and in suspended particulate matter samples collected in the Rhône River and evidenced the importance of autoxidation in the degradation of organic matter of terrestrial origin.

Characterization of the corrosion or anodic oxidation products on zinc

1975 ◽  
Vol 3 (2) ◽  
pp. 129-138 ◽  
Author(s):  
G. Trabanelli ◽  
F. Zucchi ◽  
G. Brunoro ◽  
G. Gilli
Keyword(s):  
Anodic Oxidation ◽  
Oxidation Products

scholarly journals Comparison of Cholesterol Oxidation Product Preparation Methods for Subsequent Gas Chromatographic Analysis

2004 ◽  
Vol 87 (2) ◽  
pp. 474-480 ◽  
Author(s):  
Maria Teresa Rodriguez-Estrada ◽  
Arianna Costa ◽  
Marco Pelillo ◽  
Maria Fiorenza Caboni ◽  
Giovanni Lercker
Keyword(s):  
Degradation Products ◽  
Oxidation Products ◽  
Gas Chromatography Mass Spectrometry ◽  
Cholesterol Oxidation ◽  
Preparation Methods ◽  
Mass Spectrometry System ◽  
Phase Liquid ◽  
The Stability ◽  
Layer Chromatography ◽  
Cold Saponification

Abstract An evaluation was made of the stability of cholesterol hydroperoxides (CHPs) under the analytical conditions and preparation methods commonly used for determination and quantification of cholesterol oxidation products (COPs). CHPs were prepared by photoxidation and separated by silica thin-layer chromatography. CHPs were individually collected by normal-phase liquid chromatography and then subjected either to reduction or to cold saponification. The corresponding hydroxyl derivatives were generated by reduction, whereas cold saponification gave rise predominantly to 7-ketocholesterol. In another test, silylated and non-silylated CHPs were separately injected into a gas chromatograph at 310°C, collected, and re-injected into a gas chromatography-mass spectrometry system. The silylated CHPs were more stable than the non-silylated ones, giving 7-ketocholesterol, 7α-and 7β-hydroxycholesterol as main degradation products. Two unknown degradation peaks were detected in both silylated and nonsilylated CHPs, having 384 as main m/z fragment. The study of their mass spectra led to the conclusion that peaks A and B correspond to 6α- and 6β-hydroxycholesterol, respectively.

Oxidation of nonylphenol ethoxylates in aqueous solution by UV-C photolysis, H2O2/UV-C, Fenton and photo-Fenton processes: are these processes toxicologically safe?

2013 ◽  
Vol 68 (8) ◽  
pp. 1801-1809 ◽  
Author(s):  
Akin Karci ◽  
Idil Arslan-Alaton ◽  
Miray Bekbolet
Keyword(s):  
Acute Toxicity ◽  
Vibrio Fischeri ◽  
Degradation Products ◽  
Inhibitory Effect ◽  
Oxidation Products ◽  
Treatment Processes ◽  
Nonylphenol Polyethoxylate ◽  
Uv C ◽  
Toxicity Pattern ◽  
Oxalic Acids

UV-C, H2O2/UV-C, Fenton and photo-Fenton treatment of a nonylphenol polyethoxylate (NP-10) were comparatively studied, primarily focusing on the acute toxicity of degradation products. Formic, acetic and oxalic acids were all identified as the degradation products of NP-10; however, the sole common carboxylic acid was found to be formic acid for the studied treatment processes. The percent relative inhibition towards Vibrio fischeri increased from 9% to 33% and 24% after 120 min-UV-C and H2O2/UV-C treatment, respectively. Complete NP-10 and 70% of its total organic carbon (TOC) content was removed by the photo-Fenton process, which ensured the fastest removal rates and lowest inhibitory effect (8% after 120 min treatment). The acute toxicity pattern being observed during H2O2/UV-C and photo-Fenton treatment positively correlated with temporal evolution of the identified carboxylic acids, whereas unidentified oxidation products were the most likely origin of the acute toxicity in UV-C photolysis.

Palladium-catalyzed C–H activation/C–C cross-coupling reactions via electrochemistry

2017 ◽  
Vol 53 (90) ◽  
pp. 12189-12192 ◽  
Author(s):  
Cong Ma ◽  
Chuan-Qi Zhao ◽  
Yi-Qian Li ◽  
Li-Pu Zhang ◽  
Xue-Tao Xu ◽  
...  
Keyword(s):  
Anodic Oxidation ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Chemical Oxidants ◽  
Palladium Catalyzed

Palladium-catalyzed C(sp2)–H methylation and acylation via anodic oxidation have been developed to avoid the use of stoichiometric chemical oxidants.

Sign in / Sign up

Export Citation Format

Share Document