Temperature dependence of the formation of Tris[2,3-bis(2-pyridyl)pyrazine]-iron(II)

1974 ◽  
Vol 27 (12) ◽  
pp. 2671 ◽  
Author(s):  
PJ Guerney ◽  
RJ Knight ◽  
RN Sylva
Keyword(s):  
Complex Formation ◽  
Temperature Dependence ◽  
Rate Constants ◽  
Absorption Maximum ◽  
Formation Constant ◽  
Molar Absorptivity ◽  
Dissociation Reaction ◽  
First Order ◽  
First Order Kinetics ◽  
Complex Formation Process

The overall formation constant, β3, of tris[2,3-bis(2- pyridyl)pyrazine]iron(II) was determined spectrophotometrically at 25, 40, 60 and 80�C as 8.9 x 107, 2.9 x 107, 1.0 x 107 and 1.8 x 106 (mol l-1)-3 respectively at pH > 5.5. The pKa of the ligand is 3.1 at 25�C and decreases to about 2.0 at 80�C. The variation of β3 with temperature is attributed to differences in the temperature dependence of the rate constants of the complex formation process and of dissociation. The overall energy of activation for complex formation is -870 J mol-1. The complex dissociates according to first order kinetics with rate constants of 4.3 x 10-3 s-1 and 6.8 x 10-2 s-1 at 25 and 35�C respectively, and the activation energy of the dissociation reaction is about 3000 J mol-1. The molar absorptivity of the complex, 11000 1. mol-1 cm-1 at the absorption maximum (λmax 535 nm), is independent of temperature from 25 to 80�C.

Lifetimes of the solvated electron in liquid alcohols

1977 ◽  
Vol 55 (16) ◽  
pp. 3058-3059 ◽  
Author(s):  
J. H. Baxendale ◽  
Peter Wardman
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Aliphatic Alcohols ◽  
Solvated Electron ◽  
Arrhenius Plots ◽  
First Order ◽  
First Order Kinetics

The solvated electron, es−, decays with first-order kinetics in pulse-irradiated aliphatic alcohols, attributed to reaction 1: es− + ROH → products. It is suggested that a recent report of curved Arrhenius plots for the temperature dependence of the rate constants for reaction 1 can be ascribed to reaction of es− with impurities.

A kinetic standard for precise calibration of spectrophotometer cell temperature.

1981 ◽  
Vol 27 (5) ◽  
pp. 753-755 ◽  
Author(s):  
P A Adams ◽  
M C Berman
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cell Temperature ◽  
First Order ◽  
Order Rate ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

Abstract We describe a simple, highly reproducible kinetic technique for precisely measuring temperature in spectrophotometric systems having reaction cells that are inaccessible to conventional temperature probes. The method is based on the temperature dependence of pseudo-first-order rate constants for the acid-catalyzed hydrolysis of N-o-tolyl-D-glucosylamine. Temperatures of reaction cuvette contents are measured with a precision of +/- 0.05 degrees C (1 SD).

Kinetik der Reaktion von 2.4-Dinitrofluorbenzol mit Imidazol-, SH- und Imidazol-SH-Verbindungen / Kinetics of the Reaction of 2,4-dinitro-1-fluorobenzene with Imidazole-, SH- and Imidazole-SH-compounds

1971 ◽  
Vol 26 (10) ◽  
pp. 1010-1016 ◽  
Author(s):  
Renate Voigt ◽  
Helmut Wenck ◽  
Friedhelm Schneider
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Reaction Rate ◽  
Ph Dependence ◽  
First Order ◽  
Molecular Transfer ◽  
Thiolate Anion ◽  
Nucleophilic Reactivity ◽  
Kinetics Of ◽  
Lindley Equation

First order rate constants of the reaction of a series of SH-, imidazole- and imidazole/SH-compounds with FDNB as well as their pH- and temperature dependence were determined. Some of the tested imidazole/SH-compounds exhibit a higher nucleophilic reactivity as is expected on the basis of their pKSH-values. This enhanced reactivity is caused by an activation of the SH-groups by a neighbouring imidazole residue. The pH-independent rate constants were calculated using the Lindley equation.The kinetics of DNP-transfer from DNP-imidazole to SH-compounds were investigated. The pH-dependence of the reaction displays a maximum curve. Donor in this reaction is the DNP-imidazolecation and acceptor the thiolate anion.The reaction rate of FDNB with imidazole derivatives is two to three orders of magnitude slower than with SH-compounds.No inter- or intra-molecular transfer of the DNP-residue from sulfure to imidazole takes place.

Removal of sulfonamides from wastewater in the UV/TiO2 system: effects of pH and salinity on photodegradation and mineralization

2019 ◽  
Vol 79 (2) ◽  
pp. 349-355 ◽  
Author(s):  
C. H. Wu ◽  
C. Y. Kuo ◽  
C. D. Dong ◽  
C. W. Chen ◽  
Y. L. Lin
Keyword(s):  
Rate Constants ◽  
Inhibitory Effect ◽  
Chloride Ions ◽  
Mineralization Rate ◽  
Direct Photolysis ◽  
First Order ◽  
First Order Kinetics ◽  
Lower Reactivity ◽  
Chlorine Radicals ◽  
Effects Of Ph

Abstract The effects of salinity on the photodegradation and mineralization of sulfonamides in the UV/TiO2 system were investigated. The goals of this study were to analyze the effects of pH and salinity on the sulfonamide concentration and total organic carbon (TOC) during the removal of sulfonamides in a UV/TiO2 system. Four sulfonamides – sulfadiazine (SDZ), sulfamethizole (SFZ), sulfamethoxazole (SMX) and sulfathiazole (STZ) - were selected as parent compounds. The photodegradation and mineralization rates of sulfonamides in the UV/TiO2 system satisfy pseudo-first-order kinetics. Direct photolysis degraded sulfonamides but sulfonamides cannot be mineralized. The photodegradation and mineralization rate constants in all experiments followed the order pH 5 > pH 7 > pH 9. At pH 5, the mineralization rate constants of SMX, SFZ, SDZ and STZ were 0.015, 0.009, 0.012 and 0.011 min−1, respectively. The addition of NaCl inhibited the mineralization of the four tested sulfonamides more than it inhibited their photodegradation. The inhibitory effect of chloride ions on the removal of sulfonamides in the UV/TiO2 system was attributed to the scavenging by chloride ions of hydroxyl radicals (HO•) and holes and the much lower reactivity of chlorine radicals thus formed, even though the chlorine radicals were more abundant than HO•.

Skeletal isomerization of cyclohexene on Al2O3 and AlPO4–Al2O3 catalysts

1984 ◽  
Vol 62 (8) ◽  
pp. 1455-1458 ◽  
Author(s):  
J. M. Campelo ◽  
A. Garcia ◽  
J. M. Gutierrez ◽  
D. Luna ◽  
J. M. Marinas
Keyword(s):  
Rate Constants ◽  
Reaction Pathway ◽  
Acid Sites ◽  
Skeletal Isomerization ◽  
Irreversible Adsorption ◽  
First Order ◽  
First Order Kinetics ◽  
Selectivity Studies ◽  
Apparent Activation Energies ◽  
Competitive Products

Cyclohexene skeletal isomerization, in a microcatalytic pulse reactor, was investigated using Al2O3 and AlPO4–Al2O3 as catalysts. Apparent rate constants and apparent activation energies were calculated according to the kinetic model of Bassett–Habgood. Selectivity studies concluded that 1-MCP and 3-MCP were competitive products with a first-order kinetics. The rate constants as well as the selectivity at 1-MCP increase with an increase in the number and strength of stronger acid sites, measured by means of the irreversible adsorption of aniline in cyclohexane, at 298 K, using a spectrophotometric method. The parallel reaction pathway, proposed for AlPO4 catalysts, agrees with both the observed rates and selectivities using Al2O3 and AlPO4–Al2O3 catalysts.

Kinetics of iron(III) hydrolysis and precipitation in aqueous glycine solutions assessed by voltammetry

2009 ◽  
Vol 74 (10) ◽  
pp. 1531-1542 ◽  
Author(s):  
Vlado Cuculić ◽  
Ivanka Pižeta
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Rate Constants ◽  
Glycine Concentration ◽  
First Order ◽  
Mercury Drop Electrode ◽  
Calculated Rate ◽  
Cathodic Voltammetry ◽  
Kinetics Of ◽  
Voltammetric Measurements

The kinetics of iron(III) hydrolysis and precipitation in aqueous glycine solutions were studied by cathodic voltammetry with a mercury drop electrode. The kinetics was controlled by changing ionic strength (I), pH and glycine concentration. Voltammetric measurements clearly showed formation and dissociation of a soluble Fe(III)–glycine complex, formation of iron(III) hydroxide and its precipitation. The rate constants of iron(III) hydroxide precipitation were assessed. The precipitation is first-order with respect to dissolved inorganic iron(III). The calculated rate constants of iron(III) precipitation varied from 0.18 × 10–5 s–1 (at 0.2 M total glycine, pH 7.30, I = 0.6 mol dm–3) to 2.22 × 10–3 s–1 (at 0.1 M total glycine, pH 7.30, I = 0.2 mol dm–3). At 0.5 M total glycine and I = 0.6 mol dm–3, the iron(III) precipitation was not observed.

Azides. Part V. A kinetic study of the formation of N-(p-toluenesulphonyl)-1H-azepine by thermolysis of p-toluenesulphonylazide in benzene under nitrogen pressure

1985 ◽  
Vol 63 (4) ◽  
pp. 887-890 ◽  
Author(s):  
Nagaraj R. Ayyangar ◽  
Ramesh B. Bambal ◽  
Dattatraya D. Nikalje ◽  
Kumar V. Srinivasan
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Nitrogen Pressure ◽  
Time Profile ◽  
First Order ◽  
First Order Kinetics ◽  
Concentration Time

The course of thermolysis of p-toluenesulphonylazide (A) in benzene at 160 °C and 40.1 atm of nitrogen pressure was followed by analysis of the reactants and products in the reaction mixture by hplc. The rate measurements indicate that the reaction follows first-order kinetics with respect to the formation of N-(p-toluenesulphonyl)-1H-azepine (B) and p-toluencsulphonamide (D). The concentration–time profile is consistent with the formation of p-toluenesulphonylanilide (C) from the azepine (B). The rate constants indicate that the azepine (B) decomposes to the anilide (C) at the same rate at which it is formed.

Effects of oxidant concentration and temperature on decolorization of azo dye: comparisons of UV/Fenton and UV/Fenton-like systems

2012 ◽  
Vol 65 (11) ◽  
pp. 1970-1974 ◽  
Author(s):  
C. Y. Kuo ◽  
C. Y. Pai ◽  
C. H. Wu ◽  
M. Y. Jian
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Azo Dye ◽  
Activation Energies ◽  
First Order ◽  
First Order Kinetics ◽  
Oxidant Concentration ◽  
Decolorization Efficiency ◽  
Pseudo First Order ◽  
Reactive Red 2

This study applies photo-Fenton and photo-Fenton-like systems to decolorize C.I. Reactive Red 2 (RR2). The oxidants were H2O2 and Na2S2O8; Fe2+, Fe3+, and Co2+ were used to activate these two oxidants. The effects of oxidant concentration (0.3–2 mmol/L) and temperature (25–55 °C) on decolorization efficiency of the photo-Fenton and photo-Fenton-like systems were determined. The decolorization rate constants (k) of RR2 in the tested systems are consistent with pseudo-first-order kinetics. The rate constant increased as oxidant concentration and temperature increased. Activation energies of RR2 decolorization in the UV/H2O2/Fe2+, UV/H2O2/Fe3+, UV/Na2S2O8/Fe2+ and UV/Na2S2O8/Fe3+ systems were 32.20, 39.54, 35.54, and 51.75 kJ/mol, respectively.

Pond and wetland treatment

2003 ◽  
Vol 48 (5) ◽  
pp. 1-8 ◽  
Author(s):  
R.H. Kadlec
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cost Effective ◽  
Fecal Coliforms ◽  
First Order ◽  
Loading Rates ◽  
Wetland Treatment ◽  
Long Term Performance ◽  
Term Performance

Wetlands are in use as adjuncts to wastewater treatment lagoons at many north temperate locations. Performance data for 21 systems show median removals of 67, 61, 61, 48 and 99.8% for TSS, BOD, NH4-N, TP and fecal coliforms, respectively. Hydraulic loading rates range from 0.14 to 55 cm/d, areas from 0.02 to 200 ha, and latitudes from 30 to 54°N. Calibrations of first order models with temperature dependence show that rate constants vary from seasonal dependence at low loadings to temperature dependence at high loadings for ammonia. Phosphorus rate constants display seasonal, not temperature effects. BOD and TSS are not affected by season. Wetland rate constants are larger than those for lagoons for all constituents. The optimal winter operating strategy, if hydraulics allow, is partial storage during frozen months, coupled with winter use of the wetlands. The use of FWS wetlands for polishing lagoon effluents is cost effective when land availability is not drastically constrained. Many systems have been in operation long enough to demonstrate sustainable long-term performance. Infiltration beds are potentially a valuable addition to ponds and wetlands.

Bioconcentration factors and kinetics of chlorobenzenes in a juvenile crab (Portunus pelagicus (L))

1993 ◽  
Vol 44 (4) ◽  
pp. 565 ◽  
Author(s):  
MR Mortimer ◽  
DW Connell
Keyword(s):  
Rate Constants ◽  
Aquatic Organisms ◽  
Aqueous Solubility ◽  
Portunus Pelagicus ◽  
Lipophilic Compounds ◽  
First Order ◽  
First Order Kinetics ◽  
Log Kow ◽  
Wet Weight ◽  
Depuration Rate

The uptake- and depuration-rate constants (k1 and k2 respectively), according to first-order kinetics, were measured for a series of chlorobenzenes with juvenile crabs, Portunus pelagicus. These constants were found to be related to the lipophilicity of the chlorobenzenes as expressed by the octanol-water coefficient (log Kow), giving relationships similar to those observed with fish. However, the actual magnitude of k1 and k2 on a lipid basis ranged from 720 to 5880 h-1 and from 0.492 to 0.0102 h-1 respectively, which is about ten times faster than those for fish. The bioconcentration factor (KB in wet weight units) obtained from these rate constants was related to Kow, by the following expression. log KB=-2.88+1.09 log Kow. The empirical constants in this equation are similar to those observed with other aquatic organisms except that the value of -2.88 is lower than that reported with the other organisms. This is probably due to the relatively low lipid content of the crabs. It is suggested that the bioconcentration of essentially nonbiodegradable lipophilic compounds occurs as a result of partitioning between biota lipid and water. Other physicochemical properties (molar volume and aqueous solubility) and two molecular descriptors (zero- and first-order Randik indices) exhibited good correlations with the bioconcentration characteristics described above.

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