Unusual Decomposition Research Articles

Kinetic investigations into the copper(II)-catalysed peroxosulfate oxidation of Calmagite dye in alkaline media

Addition of CuII catalysed the peroxosulfate (KHSO5) oxidation of Calmagite dye (D) in alkaline media and it was observed that the dye decomposition profiles exhibit extremely complex kinetic behaviour, with typical induction periods associated with rapid autocatalysis. A comprehensive kinetic model has been derived which not only can predict changes in speciation of reactants with time, but can also satisfactorily explain all the kinetic profiles. Much higher catalyst concentrations are required for copper(II) catalysis than for manganese(II) catalysis ([KHSO5] > [CuII] > [D] as opposed to [KHSO5] > [D] > [MnII]), i.e. there needs to be excess CuII over D. This arises for two main reasons; first, binding of CuII to the dye inhibits its reaction with peroxosulfate, protecting the dye against oxidation, and secondly the active catalyst is a heterogeneous copper hydroxide species which arises when there is an excess of CuII in alkaline media. The unusual decomposition profiles are attributed to release of CuII into alkaline media via direct oxidation of the [CuD] complex by peroxosulfate. This oxidation is relatively slow, but when sufficient CuII is released ‘true’ autocatalysis is exhibited. The best simulated fits were obtained when the catalytic step was assumed to be first order in [SO52–] (i.e. peracid primarily acting as a nucleophile) and zero order in [CuD] as it is adsorbed onto the colloidal copper hydroxide.

Preparation and unusual decomposition of silica-supported tetraphenylphosphonium bromide

Amorphous silica gel grafted with a directly bound tetraarylphosphonium salt has been prepared and has been characterised by 13C CP MAS NMR, DRIFTS and elemental microanalysis. Thermal analysis of this material reveals a strikingly different decomposition pattern to its unsupported analogue: free tetraphenylphosphonium bromide obeys pseudo-zeroth-order kinetics, with Ea= 204 ± 16 kJ mol–1, ΔH‡= 206 ± 16 kJ mol–1 and ΔS‡=–87 ± 25 J K–1 mol–1, whereas the supported reagent shows a first-order decay, with Ea= 77 ± 22 kJ mol–1, ΔH‡= 72 ± 22 kJ mol–1 and ΔS‡=–197 ± 34 J K–1 mol–1. Evolved-gas mass spectrometry shows that the supported tetraarylphosphonium salt shows a greater propensity to eliminate triphenylphosphine than would be expected from purely statistical considerations. This material shows 13C CP MAS NMR and decomposition characteristics more typical of the solution state than the solid phase.

Thermolysis of 3,3-Bis(phenylmethyl)-1,2-dioxetane: Radical-Induced Formation of the Unusual Decomposition Product 3-Phenyl-1-(phenylmethoxy)-2-propanone

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermolysis of 3,3-Bis(phenylmethyl)-1,2-dioxetane: Radical-Induced Formation of the Unusual Decomposition Product 3-Phenyl-1-(phenylmethoxy)-2-propanoneWaldemar Adam and Simone AndlerCite this: J. Am. Chem. Soc. 1994, 116, 13, 5674–5678Publication Date (Print):June 1, 1994Publication History Published online1 May 2002Published inissue 1 June 1994https://doi.org/10.1021/ja00092a019RIGHTS & PERMISSIONSArticle Views96Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (601 KB) Get e-Alerts Get e-Alerts

Die Fluorsulfine XF2C(F)C  SO (X = F, Cl, Br), ihre Synthese und ungewöhnliche Zersetzungsart

The Fluorosulfines XF2C(F)C  SO (X = F, Cl, Br), Their Synthesis and Unusual Type of DecompositionA new route for the synthesis of the sulfenyl chloride 3 opens an easy access to fluoro(trifluoromethyl)sulfine (6) by hydrolysis of 3, trapping 6 by Diels‐Alder reaction with anthracene, and thermolysis of the formed compound 8. By addition of the thioacetyl fluorides XF2C(F)C  S (X = Cl, Br) to anthracene compounds 9a, b are obtained, which could be oxidized to the sulfene adducts 12a, b as well as to the sulfine adducts 13a, b. Thermolysis of the latter yields the sulfines 17a, b, which are unstable at room temperature. A second approach to 17a involves oxidation of 1,3‐dithietane 11a to its S‐oxide 14a (e.g. via an S,S‐difluoro compound 15a) and subsequent thermolysis, but thermal decomposition predominates. An unusual decomposition has been observed for 17a, b which was hitherto unknown for sulfines.

Acetate formation and explosive decomposition during ethanol oxidation on Rh

The adsorption and reaction of ethanol with the Rh(110) surface has been studied using a thermal molecular beam system and temperature programmed desorption. On the clean surface, ethanol shows a very simple dehydrogenation, producing hydrogen in the gas phase, adsorbed CO (which is desorbed by heating to 550 K) and carbon. Since in alcohol synthesis reactions it is likely that the surface will be partially oxidised, the reaction with predosed oxygen was also investigated. The reaction pathway then becomes much more complex. The main changes are (i) CH4 and H2O evolution during adsorption, and (ii)Acetate formation by oxygen insertion in the molecule. The acetate shows very unusual decomposition kinetics — a surface ‘explosion’ with a very narrow peak-yielding CO2 and H2 in the gas phase and adsorbed C. The acetate is always seen on Rh catalysts which are selective for alcohol synthesis from CO and H2, and it is proposed that oxidic promoters such as vanadia may act to stabilise this intermediate.

Decomposition of 1-nitroso-1-alkyl-3-(2-hydroxyalkyl)ureas

Nitrosoureas are compounds of increasing interest due to their carcinogenic and mutagenic activities and for their therapeutic properties in the treatment of cancer. During the course of these studies, it was necessary to synthesize 1-nitroso-1-methyl-3-(2-hydroxyethyl)urea (1) and nitroso-1-(2-hydroxyethyl)-3-methylurea (2). Nitrosation of 1-methyl-3-(2-hydroxyethyl)urea with nitrous acid gave a mixture of 1 and 2 in a 9:1 ratio. Although the mixture decomposed slowly as a neat oil, the pure major isomer 1 was stable in acetone, or ethyl acetate, solution. However, this compound decomposed explosively when in it was handled in its crystalline form, with evolution of nitrogen. Further studies of 1 were abandoned due to its explosive nature; however, the compound's unusual decomposition prompted the authors to look at one of its stable analogues, 1-nitroso-1-ethyl-3-(2-hydroxyethyl)urea. In summary, 1-(nitrosoalkyl)-3-(2-hydroxyalkyl)ureas break under neutral conditions to the corresponding 2-ozazolidone and the alkldiazonium ion. These reactions take place via a nucleophilic attack by the hydroxyl group of the electrophilic urea carbonyl to give a hemiacetal intermediate.

Thermolysis of 7,8-dioxabicyclo[4.2.2]deca-2,4,9-trienes. An unusual decomposition mode of endoperoxides

Thermolysis of 7,8-dioxabicyclo[4.2.2]deca-2,4,9-trienes. An unusual decomposition mode of endoperoxides

Some Aspects of the Reaction between Chitosan and Formaldehyde

Abstract Reactions of chitosan (degree of deacetylation 67%, weight-average molecular weight 850,000) with formaldehyde were performed in a dilute aqueous acetic acid solution at a molar ratio of amino groups of the polymer to HCHO of 0.06:O.1 mol/L and at different temperatures (45, 60, and 75°C). In each case the pH of the reaction mixtures was 3.4 during the experiments. The process was investigated by measuring the kinetic changes of the free formaldehyde concentration and the sum of free formaldehyde and methylol groups produced. No gelation of the reaction product was observed. The experimental results led to the conclusion that the methylol groups formed by the addition of HCHO to chitosan functions take part in some intramolecular reactions with amino and/or hydroxyl groups of chitosan. Initially, the concentration of the resultant methylene bridges grows rapidly and then drops again until an equilibrium is established. This rather unusual decomposition of the methylene links once formed without changing the reaction conditions is accompanied by a substantial growth of the amount of methylol derivative whose concentration at the beginning of the process increased rather slowly.

Notiz zum massenspektrometrischen Zerfall monohalogenierter Essigsäuren und Essigsäureester. 36. Mitteilung über massenspektrometrische Untersuchungen

Note on the Mass Spectral Decomposition of Monohalogenated Acetic Acids and its EstersBesides the well known ester fragmentation reactions two unusual decomposition reactions are observed in the mass spectra of the title compounds, leading to the ions [M‐CO2]+ and [M‐HX]+. The rearrangement reactions involved in the formation of these ions are discussed.

Influence of applied electric fields on the free radical copolymerization of methylmethacrylate and styrene. An unusual decomposition of benzoylperoxide

The influence of an applied electric field on the free radical copolymerization of methylmethacrylate (MMA) and styrene (ST) in benzene solution was investigated. With benzoylperoxide as initiator, retardation of the polymerization of MMA was observed in the cathode compartment, whereas the polymerization of ST and the copolymerization of MMA and ST in the anode compartment were unaffected. No such effects were found when azobisisobutyronitrile was the initiator. The effect of the electric field on the polymerization of MMA was attributed to the effect of oxygen formed at the cathode by decomposition of benzoylperoxide in an electrolytic redox reaction that also produced [graphic omitted] and [graphic omitted] together with the products of the thermal decomposition.

Ethylene adduct of conjugated octadecadienoic acids: II. Ozonization products

AbstractMethyl 8‐(4‐n‐hexylcyclohex‐2‐enyl) octanoate obtained by esterifying the adduct of ethylene andtrans,trans‐9,11‐octadecadienoic acid was ozonized in methanol as a participating solvent. The resultant cyclic methoxyhemiperacetal was reduced with powdered zinc to the dialdehyde, methyl 9,12‐diformylstearate, which was isolated as the tetramethyldiacetal. This dialdehyde readily air‐oxidizes to give methyl 9,12‐dicarboxystearate. Heating the cyclic methoxyhemiperacetal slowly from 25 to 100 C in vacuo results in an unusual decomposition reaction which gives hydrogen and methyl 9 (12)‐carbomethoxy‐12(9)‐carboxystearate as the primary products and methyl 9 (12)‐carbomethoxystearate as the major by‐product. Treatment of the cyclic hemiperacetal with hydrogen peroxide in formic acid gave unexpectedly dihydroxystearic acid as one of the products.

An unusual decomposition of the dianion of benzophenone azine

An unusual decomposition of the dianion of benzophenone azine