Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 895-902
Author(s):  
Clifford A Bunton ◽  
Houshang J Foroudian ◽  
Nicholas D Gillitt ◽  
Anurag Kumar
Keyword(s):  
Hydrogen Peroxide ◽  
Ion Exchange ◽  
Rate Constants ◽  
Acid Catalysis ◽  
Sulfide Oxidation ◽  
Methanesulfonic Acid ◽  
Effective Catalyst ◽  
First Order ◽  
Mineral Acids ◽  
Electron Donation

Oxidations of sulfides and phosphorus(V) esters of thiols by H2O2 are catalyzed by H2SO4 and HClO4. Sulfides are 4-ZC6H4SMe, 1a-1e, respectively, Z = MeO, Me, H, Cl, NO2; PhSCH2CH2Cl, 2, Ph2S, 3, and the esters are Ph(R)PO·SEt, 4a, 4b, R = Ph, EtO. Electron donation by Z moderately accelerates reaction, but the sulfides are much more reactive than the esters. Reactions are first order in H2O2 and substrate, and second-order rate constants, k2, in H2SO4 are related to excess acidity, X. Plots of log k2 against X have slopes in the range 0.61-0.85. Rate constants are similar for given concentrations of H2SO4 and HClO4, except that with greater than 50 wt.% H2SO4 peroxymonosulfuric acid is formed and the observed rate constants then increase. Methanesulfonic acid is a less effective catalyst than the mineral acids. Oxidations of the sulfides are also catalyzed by strongly acidic ion-exchange resins.Key words: sulfide oxidation, hydrogen peroxide, acid catalysis, excess acidity.

Direkte Bestimmung der Geschwindigkeitskonstanten des Durchtritts vom kleinen zum großen Hohlraumsystem im Molekularsieb Typ 13 X für Sr-und Ba-Ionen / Direct Determination of the Rate Constants for the Sr- and Ba-exchange Between the Small and Large Channels in LMS 13 X

1975 ◽  
Vol 30 (8) ◽  
pp. 951-954 ◽  
Author(s):  
K. Frohnecke ◽  
H. Fischbach
Keyword(s):  
Ion Exchange ◽  
Rate Constants ◽  
Diffusion Coefficients ◽  
Large Diameter ◽  
Direct Determination ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Total Exchange

Abstract Direct Determination of the Rate Constants for the Sr-and Ba-exchange Between the Small and Large Channels in LMS 13X The rate constants for the intracristalline Sr-and Ba-exchange between the small and large diameter channels of LMS 13X were measured. For this matter the method of interrupting the ion exchange was modified. It is assumed, that a first order reaction takes place. Using the rate constants and the diffusion coefficients, which were measured by Hoinkis and Levi, the total exchange of Sr 2+ and Ba 2+ could be calculated.

Kinetic studies of Dakin oxidation of o- and p-hydroxyacetophenones

1977 ◽  
Vol 55 (1) ◽  
pp. 102-110 ◽  
Author(s):  
M. B. Hocking ◽  
J. H. Ong
Keyword(s):  
Hydrogen Peroxide ◽  
Fractional Order ◽  
Rate Constants ◽  
Kinetic Studies ◽  
Second Order ◽  
Simple Test ◽  
Alkaline Hydrogen Peroxide ◽  
Para Isomer ◽  
First Order ◽  
Pseudo First Order

Rates of oxidation of aqueous o-, and p-hydroxyacetophenone with alkaline hydrogen peroxide to yield catechol and hydroquinone, respectively, have been followed spectrophotometri-cally. Both ketones showed smooth pseudo first-order behaviour, the ortho isomer yielding rate constants in the range 2.6 to 6.6 × 10−2 min−1 at 0 °C, and the para isomer of 0.73 to 7.10 × 10−2 min−1 at 35 °C for the concentrations of hydrogen peroxide and base used. The order in hydrogen peroxide was, unexpectedly, found to be 1.4. A simple test established that this fractional order was probably not the result of hydrogen peroxide involvement in simultaneous first- and second-order processes of differing rates. Other plausible pathways to explain this are proposed.

The sterilizing effect againstBacillus subtilisspores of hydrogen peroxide at different temperatures and concentrations

1968 ◽  
Vol 35 (3) ◽  
pp. 423-428 ◽  
Author(s):  
P. Swartling ◽  
B. Lindgren
Keyword(s):  
Hydrogen Peroxide ◽  
Bacillus Subtilis ◽  
Rate Constant ◽  
Rate Constants ◽  
Death Rate ◽  
Survival Curves ◽  
First Order ◽  
Commercial Practice ◽  
Different Temperatures ◽  
Experimental Findings

SummaryAn investigation was made of the death-rate ofBacillus subtilisspores in suspension in hydrogen peroxide concentrations of 10, 15 and 20% at 25, 50, 60, 70 and 80°C. Average logarithmic survival curves were plotted against normal time and death-rate constants andQ10values were calculated from the graphically determined decimal reduction times. This treatment of the experimental findings was found to be warranted in the temperature range 60–80°C. The first-order death-rate constant was ∽ 0·1 s−1for 10% hydrogen peroxide solution at 60°C and theQ10was about 1·6. Increases in the concentration from 10 to 15% and from 15 to 20% each gave an increase of about 50% in the rate constant. The application of these data to commercial practice is discussed.

scholarly journals Dephosphorylation of pig heart pyruvate dehydrogenase phosphate complexes by pig heart pyruvate dehydrogenase phosphate phosphatase

1981 ◽  
Vol 195 (1) ◽  
pp. 51-59 ◽  
Author(s):  
A L Kerbey ◽  
P J Randle ◽  
A Kearns
Keyword(s):  
Ion Exchange ◽  
Pyruvate Dehydrogenase ◽  
Rate Constants ◽  
Gel Filtration ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Initial Burst ◽  
First Order ◽  
Order Rate ◽  
Crude Preparation

1. Pig heart pyruvate dehydrogenase phosphate complex in which all three sites of phosphorylation were completely phosphorylated was re-activated at a slower rate by phosphatase than complex predominantly phosphorylated in site 1. The ratio of initial rates of re-activation was approx. 1:5 with a comparatively crude preparation of phosphatase and with phosphatase purified by gel filtration and ion-exchange chromatography. 2. The ratio of apparent first-order rate constants during dephosphorylation of fully phosphorylated complex averaged 1/3.8/1.3 for site 1/site 2/site 3. Only site-1 dephosphorylation was linearly correlated with re-activation of the complex throughout dephosphorylation. Dephosphorylation of site 3 was linearly correlated with re-activation after an initial burst of dephosphorylation. 3. Because dephosphorylation of site 1 was always associated with dephosphorylation of site 2, it is concluded that dephosphorylation cannot be purely random. 4. The ratio of apparent first-order rate constants for dephosphorylation of site 1 (partially/fully phosphorylated complexes) averaged 1.72. This ratio is smaller than the ratio of approx. 5 for the initial rates of re-activation. Possible mechanisms involved in the diminished rate of re-activation of fully phosphorylated complex are discussed.

scholarly journals Kinetic measurements of the reactivity of hydrogen peroxide and ozone towards small atmospherically relevant aldehydes, ketones and organic acids in aqueous solutions

2014 ◽  
Vol 14 (9) ◽  
pp. 4503-4514 ◽  
Author(s):  
L. Schöne ◽  
H. Herrmann
Keyword(s):  
Hydrogen Peroxide ◽  
Rate Constants ◽  
Radical Reaction ◽  
Degradation Process ◽  
Atmospheric Environment ◽  
Radical Reactions ◽  
Kinetic Measurements ◽  
First Order ◽  
Reaction Rate Constants ◽  
Vis Spectroscopy

Abstract. Free radical reactions are an important degradation process for organic compounds within the aqueous atmospheric environment. Nevertheless, non-radical oxidants such as hydrogen peroxide and ozone also contribute to the degradation and conversion of these substances (Tilgner and Herrmann, 2010). In this work, kinetic investigations of non-radical reactions were conducted using UV / Vis spectroscopy (dual-beam spectrophotometer and stopped flow technique) and a capillary electrophoresis system applying pseudo-first order kinetics to reactions of glyoxal, methylglyoxal, glycolaldehyde, glyoxylic, pyruvic and glycolic acid as well as methacrolein (MACR) and methyl vinyl ketone (MVK) with H2O2 and ozone at 298 K. The measurements indicate rather small rate constants at room temperature of k2nd < 3 M−1 s−1 (except for the unsaturated compounds exposed to ozone). Compared to radical reaction rate constants the values are about 10 orders of magnitude smaller (kOH&amp;bullet; ~109 M−1 s−1). However, when considering the much larger non-radical oxidant concentrations compared to radical concentrations in urban cloud droplets, calculated first-order conversion rate constants change the picture towards H2O2 reactions becoming more important, especially when compared to the nitrate radical. For some reactions mechanistic suggestions are also given.

Performance and Modelling of a Highway Wet Detention Pond Designed for Cold Climate

2009 ◽  
Vol 44 (3) ◽  
pp. 253-262 ◽  
Author(s):  
Jes Vollertsen ◽  
Svein Ole Åstebøl ◽  
Jan Emil Coward ◽  
Tor Fageraas ◽  
Asbjørn Haaning Nielsen ◽  
...  
Keyword(s):  
Rate Constants ◽  
Pond Water ◽  
Pollutant Removal ◽  
Cold Climate ◽  
Traffic Load ◽  
Substantial Part ◽  
First Order ◽  
Detention Pond ◽  
Time Of Year ◽  
Wet Detention Pond

Abstract A wet detention pond in Norway has been monitored for 12 months. The pond receives runoff from a highway with a traffic load of 42,000 average daily traffic. Hydraulic conditions in terms of inflow, outflow, and pond water level were recorded every minute. Water quality was monitored by volume proportional inlet and outlet samples. During most of the year, excellent pollutant removal was achieved; however, during two snowmelt events the pollutant removal was poor or even negative. The two snowmelt events accounted for one third of the annual water load and for a substantial part of the annual pollutant discharge. The performance of the pond was analyzed using a dynamic model and pollutant removal was simulated by first-order kinetics. Good agreement between measurement and simulation could be achieved only when choosing different first-order rate constants for different parts of the year. However, no relation between the rate constants obtained and the time of year could be identified, and neither did the rate constants for different pollutants correlate. The study indicates that even detailed measurements of pollutant input and output allow only average performance to be simulated and are insufficient for simulating event-based variability in pond performance.

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (&lt; 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

scholarly journals Kinetics and Mechanism of the Change of the 4-Nitrobenzylthio-System into 4,4′-Diformylazoxybenzene in Alkaline Dioxane-Water Media

1985 ◽  
Vol 40 (11) ◽  
pp. 1128-1132
Author(s):  
Y. Riad ◽  
Adel N. Asaad ◽  
G.-A. S. Gohar ◽  
A. A. Abdallah
Keyword(s):  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Main Product ◽  
Reaction Medium ◽  
Aqueous Dioxane ◽  
Proton Abstraction ◽  
First Order ◽  
Water Media ◽  
Different Temperatures

Sodium hydroxide reacts with α -(4-nitrobenzylthio)-acetic acid in aqueous-dioxane media to give 4,4'-diformylazoxybenzene as the main product besides 4,4'-dicarboxyazoxybenzene and a nitrone acid. This reaction was kinetically studied in presence of excess of alkali in different dioxane-water media at different temperatures. It started by a fast reversible a-proton abstraction step followed by two consecutive irreversible first-order steps forming two intermediates (α -hydroxy, 4-nitrosobenzylthio)-acetic acid and 4-nitrosobenzaldehyde. The latter underwent a Cannizzaro's reaction, the products of which changed in the reaction medium into 4,4'-diformylazoxybenzene and 4,4'-dicarboxyazoxybenzene. The rate constants and the thermodynamic parameters of the two consecutive steps were calculated and discussed. A mechanism was put forward for the formation of the nitrone acid.Other six 4-nitrobenzyl, aryl sulphides were qualitatively studied and they gave mainly 4,4'-diformylazoxybenzene beside 4,4'-dicarboxyazoxybenzene or its corresponding azo acid.

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