Search results for "Autocatalysis"
showing 10 items of 13 documents
Molecular Diversity Required for the Formation of Autocatalytic Sets
2019
Systems chemistry deals with the design and study of complex chemical systems. However, such systems are often difficult to investigate experimentally. We provide an example of how theoretical and simulation-based studies can provide useful insights into the properties and dynamics of complex chemical systems, in particular of autocatalytic sets. We investigate the issue of the required molecular diversity for autocatalytic sets to exist in random polymer libraries. Given a fixed probability that an arbitrary polymer catalyzes the formation of other polymers, we calculate this required molecular diversity theoretically for two particular models of chemical reaction systems, and then verify …
Cure behaviour of epoxy resin matrices for carbon fibre composites
1999
The cure behaviour of two resin formulations (with high and low curing agent content respectively) of an epoxy resin system, used as matrix for carbon fibre composites, was studied through calorimetric analysis. The aim of this work is to investigate the kinetics of this specific epoxy system in order to be able to choose a proper set of processing parameters which will give good composite material properties. The shape of the conversion curves gives evidence of the differences in the cure kinetics of the two systems. Furthermore, the values of the activation energies were determined both for formulation in the conversion range where vitrification occurs, following a phenomenological approa…
Kinetics of the permanganate oxidation of formic acid in aqueous solution
1987
The kinetics of the permanganate oxidation of formic acid in aqueous perchloric acid at 30°C were examined by the spectrophotometric method. The chemical reaction 2MnO + 3HCOOH + 2H+ 2MnO2 + 3CO2 + 4H2O, appears to proceed via several parallel reactions. The overall rate equation has been obtained by using statistical multilinear regression analysis of the 660 cases studied, and the presence in the rate equation of two new terms in relation to previous studies shows that both permanganate autocatalytic effects and acid media inhibition must be taken into account when the reaction proceeds at constant ionic strength.
Über Hydroxy‐linolsäuremethylester und die Umsetzung von Linolsäuremethylester mit N‐Bromsuccinimid
1962
Hydroxy-linolsauremethylester wird durch selektive Reduktion von Linolsauremethylester-hydroperoxyd mit Na-Sulfit u. a. dargestellt. Die Autoxydation des Hydroxy-linolsauremethylesters verlauft nicht autokatalytisch und ist nach Aufnahme von 1 Mol Sauerstoff pro Mol Substanz nahezu beendet. Die Reaktionsprodukte sind relative niedermolekular. Die Reaktion von Linolsauremethylester mit N-Bromsuccinimid konnte durch Umsetzung des instabilen Reaktionsproduktes mit Silbernitrat weitgehend aufgeklart werden. About Hydroxy Methyl Linoleate and the Reaction of Methyl Linoleate with N-Bromosuccinimide Hydroxy methyl linoleate is prepared by selective reduction of methyl linoleate hydroperoxyde with…
Über die autoxydation des syndiotaktischen polypropylens
1964
Bei der Autoxydation des syndiotaktischen Polypropylens in Losung lost ein monofunktioneller Zerfall der entstehenden Hydroperoxidgruppen den Kettenstart und die Autokatalyse der Radikalkettenreaktion aus. Die Ergebnisse bestatigen die Vorstellungen uber den Aufbau syndiotaktischer Polymer. Mit Hilfe der Autoxydation ist eine Unterscheidung zwischen syndiotaktischem und isotaktischem Polypropylen moglich. Chain initiation and autocatalysis of the radical chain reaction in the autoxidation of syndiotactic polypropylene is produced by the monofunctional decomposition of the hydroperoxide groups formed. The results confirm the conceptions on the structure of syndiotactic polymers. Autoxidation…
Die autoxydation von linolsäuremethylesterhydroperoxyd. Über die autoxydation ungesättigter verbindungen. XIII. Mitteilung
1961
Linolsauremethylesterhydroperoxyd wurde mit Hilfe der O'KEEFFE-Verteilung aus autoxydiertem Linolsauremethylester isoliert. Die Autoxydation dieses Hydroperoxydes verlauft rascher als die des Linolsaureesters. Die Reaktion verlaft aber nicht autokatalytisch und ist nach Aufnahme von 1 Mol Sauerstoff pro Mol Hydroperoxyd praktisch beendet; die Hydroperoxydgruppen bleiben dabei zum grosten Teil erhalten, die konjugierten Doppelbindungen verschwinden. Die Aktivierungsenergie dieser Reaktion ist um 3 kcal/Mol kleiner als die der Autoxydation des Linolsauremethylesters. Es wird ein Mechanismus vorgeschlagen, bei dem das Linolsauremethylesterhydroperoxyd hauptsachlich in biomolekularer Startreakt…
Front propagation in the one-dimensional autocatalyticA+B→2Areaction with decay
1999
We consider front propagation in the autocatalytic scheme $A+\stackrel{\ensuremath{\rightarrow}}{B}2A,$ where we also allow the A particles to decay, $\stackrel{\ensuremath{\rightarrow}}{A}0,$ with a constant decay rate $\ensuremath{\beta}.$ In a one dimensional, discrete, situation the A domain moves as a pulse, and its dynamics differs from what is found in higher dimensions. Thus the velocity of the pulse tends to a finite value when $\ensuremath{\beta}$ approaches from below the critical value ${\ensuremath{\beta}}_{c},$ at which pulses die out. On the other hand, when approaching ${\ensuremath{\beta}}_{c}$ from above, the mean lifetime of the pulse grows as $T\ensuremath{\propto}(\ensu…
Towards the design of organocatalysts for nerve agents remediation: The case of the active hydrolysis of DCNP (a Tabun mimic) catalyzed by simple ami…
2015
We report herein a study of the hydrolysis of Tabun mimic DCNP in the presence of different amines, aminoalcohols and glycols as potential suitable organocatalysts for DCNP degradation. Experiments were performed in CD3CN in the presence of 5% D2O, which is a suitable solvent mixture to follow the DCNP hydrolysis. These studies allowed the definition of different DCNP depletion paths, resulting in the formation of diethylphosphoric acid, tetraethylpyrophosphate and phosphoramide species as final products. Without organocatalysts, DCNP hydrolysis occurred mainly via an autocatalysis path. Addition of tertiary amines in sub-stoichiometric amounts largely enhanced DCNP depletion whereas non-te…
Superoxide-driven autocatalytic dark production of hydroxyl radicals in the presence of complexes of natural dissolved organic matter and iron.
2019
Abstract We introduced superoxide as potassium superoxide (KO2) to artificial lake water containing dissolved organic matter (DOM) without or with introduced ferric iron complexes (DOM-Fe(III)), and monitored the production rate of hydroxyl radicals as well as changes in the absorption and fluorescence properties of DOM. The introduction of KO2 decreased the absorption by DOM but increased the spectral slope coefficient of DOM more with complexed ferric Fe than without it. The introduction of KO2 increased the fluorescence of humic-like components in DOM without introduced ferric Fe but resulted in the loss of fluorescence in DOM with introduced ferric Fe. A single introduction of 13 μmol L…
Study of the ZnO crystal growth by vapour transport methods
2004
Abstract The crystal growth of ZnO by vapour transport is classically made with the assistance of additional species that produce a gaseous mixture, the role of which remains often uncertain in the transport and growth process. Initially, in order to study the mass transport process, a numerical simulation is made to analyse which are the requirements to have an effective transport. As the pressure of each gaseous species is generally unknown, the numerical study has been performed for different total pressures. It is found that, if congruent and equilibrium conditions are assumed at the sublimation and crystallisation interfaces, effective growth conditions can only be attained for a narro…