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  • Microemulsions  (1)
  • N-Nitroso-N-methylurea  (1)
  • N-Nitrosomorpholine  (1)
  • 1
    ISSN: 1434-4475
    Keywords: Kinetic study ; N-Methylurea ; Nitrosation ; N-Nitroso-N-methylurea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of nitrosation of Methylurea (MU) in aqueous perchloric solution has been studied using two techniques: a dynamic spectrophotometric and a stopped-flow technique. The rate law obtained, whenpH was varied in the range 0.27–3.22, is $$---d[nitrite]/dt = f[MU][nitrite][H^ + ]/(1 + g/[H^ + ])$$ where [MU] and [nitrite] represent stoichiometric concentrations. At 288.0 K and μ=1.0M,f=(15.6±0.5)M −2s−1 andg=(1.06±0.08) 10−3 M. This rate law becomes independent of the acidity of the solution when this is increased ([ClO4H])〉1.00M). These results together with the activation of the nitrosation rate by the ionic strength and the negative value of the activation entropy shown that only the NO2H2 + or NO+ is the effective carrier for the nitrosation. Comparisons with the nitrosation of dimethylamine were also made leading to the conclusion that there is no simple explanation for the fact that the nitrosation via NO2H2 +/NO+ disappears when the nitrosable compound is of increased basicity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 123 (1992), S. 383-389 
    ISSN: 1434-4475
    Keywords: Microemulsions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird eine einfache Methode zur Abschätzung von Aggregationszahl und Core-Radius von Mikroemulsionen aus Gewichtsmessungen von Natriumbis-2-ethylhexylsulphosuccinat (aerosol-OT oderAOT)/Decan/Wasser-Mikroemulsionen verschiedener Zusammensetzung vorgeschlagen. Unter den Annahmen, daß (i) die Dichte von Wasser innerhalb der Aggregationen die gleiche als bei freiem Wasser ist, (ii) das ganze Emulsionsmittel in der Grenzfläche vorliegt und (iii) das Eindringen der organischen Phase in die Grenzfläche vernachlässigbar ist, können Werte für Aggregationszahlen und Core-Radien erhalten werden, die durchaus mit entsprechenden Werten aus aufwendigeren Methoden vergleichbar sind. Das Leistungsverhältnis (Ergebnisse/geringer Aufwand) ist sehr vorteilhaft und macht die Methode für kinetische Arbeiten zur Bestimmung von Reaktionsmechanismen in Mikroemulsionen interessant.
    Notes: Summary A simple working method for the estimation of the aggregation numbers and core radii from weight measurements of sodium bis-2-ethylhexylsulphosuccinate (aerosol-OT orAOT)/decane/water microemulsions of several compositions is proposed. Starting out from the hypotheses that (i) the density of the water inside the droplets is the same as that of free water, (ii) all the surfactant is localized as interface, and (iii) the penetration of the organic phase into the interface is negligible, values for the aggregation number and core radii comparable to those determined using more sophisticated methods were obtained. The results/methodological simplicity ratio may be of great advantage in kinetic work on reaction mechanisms in microemulsions.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-4475
    Keywords: Acetate buffer ; Kinetics of nitrosation ; Morpholine ; N-Nitrosomorpholine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde die Kinetik der Nitrosierung von Morpholin in Acetat-Puffer untersucht. Unter den gewählten Reaktionsbedingungen ist das effektive Agens N2O3, dessen Bildung von Acetat-Ionen im Einklang mit dem gezeigten Schema gefördert wird: Zwischen Nitrosylacetat und Amin wurde keine Reaktion beobachtet, vermutlich wegen der niederen Konzentration des ersteren. Der vorgeschlagene Mechanismus erklärt, daß keine Katalyse mittels Puffer unter Bedingungen zu beobachten ist, wo der geschwindigkeitsbestimmende Schritt die Reaktion von N2O3 mit dem Amin ist und daß der katalytische Effekt nur dann beobachtet wird, wenn die Bildung des Nitrosierungsagens geschwindigkeitsbestimmend ist. Gleichgewichts- und kinetische Konstanten, die für den Mechanismus von Bedeutung sind, wurden ermittelt.
    Notes: Abstract The kinetics of the nitrosation of morpholine in acetate buffer have been studied. It was found that in the experimental conditions used the effective nitrosating agent is dinitrogen trioxide, whose formation is promoted by the acetate ion in accordance with the scheme: No reaction between nitrosyl acetate and the a mine was observed, probably owing to the low concentration of the former. The proposed mechanism explains the experimental facts that no catalysis by the buffer is observed in conditions in which the rate controlling step is the reaction of N2O3 with the amine, and that the catalytic effect has only been observed when the formation of the nitrosating agent is also rate controlling. Values have been calculated for several equilibrium and kinetic constants involved in the mechanism proposed.
    Type of Medium: Electronic Resource
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