Spin trapping for hydroxyl in water: a kinetic evaluation of two popular traps

1980 ◽  
Vol 58 (8) ◽  
pp. 803-807 ◽  
Author(s):  
Paul R. Marriott ◽  
M. John Perkins ◽  
David Griller
Keyword(s):  
Rate Constants ◽  
Half Life ◽  
Biological Systems ◽  
Spin Trapping ◽  
Order Process ◽  
Kinetic Evaluation ◽  
Spin Traps ◽  
First Order ◽  
Tert Butyl

Two spin traps, 4-(N-methylpyridinium)tert-butyl nitrone (4-MePyBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) were examined for their effectiveness at trapping hydroxyl in water. At pH 6 and 22 °C, rate constants for trapping hydroxyl were found to be 0.5 × 109 M−1 s−1 (4-MePyBN) and 2.0 × 109 M−1  s−1 (DMPO). The hydroxyl adduct of DMPO decayed by a first order process with a half-life of 870 s. This was at least three times greater than that of the 4-MePyBN adduct. These and other results suggest that DMPO is the superior trap for this particular application and is well suited for use in biological systems.

Kinetic Evaluation of Spin Trapping Rate Constants of New CYPMPO-type Spin Traps for Superoxide and Other Free Radicals

2015 ◽  
Vol 229 (3) ◽  
Author(s):  
Yoshimi Sueishi ◽  
Erisa Kamogawa ◽  
Hideo Nakamura ◽  
Mitsuko Ukai ◽  
Michio Kunieda ◽  
...  
Keyword(s):  
Free Radicals ◽  
Rate Constants ◽  
Spin Trapping ◽  
Trapping Rate ◽  
Kinetic Evaluation ◽  
Spin Traps

AbstractCYPMPO (5-(2,2-dimethyl-1,3-propoxyl cyclophosphoryl)-5-methyl-1-pyrroline

An Electron Spin Resonance Study of Some Reactions of Pentafluorosulfuranyl (SF5)

1975 ◽  
Vol 53 (16) ◽  
pp. 2361-2364 ◽  
Author(s):  
John Charles Tait ◽  
James Anthony Howard
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Rate Constants ◽  
Arrhenius Equation ◽  
Kinetic Studies ◽  
Electron Spin Resonance Study ◽  
Order Process ◽  
First Order ◽  
Spin Resonance ◽  
Spin Resonance Study

A kinetic electron spin resonance study of the self-reaction of SF5 and a spectroscopic and kinetic e.s.r. study of the reaction of SF5 with 1,1-di-t-butylethylene are reported. This radical undergoes self-reaction by a second-order process and the rate constants are given by the Arrhenius equation log 2k1(M−1 s−1) = (10.3 ± 0.5) − (1.7 ± 0.5)/θ where θ = 2.303RT kcal mol−1. It adds to 1,1-di-t-butylethylene to give (t-Bu)2CCH2SF5 which decomposes by a first-order process with rate constants that obey the expression log k2(s−1) = (13 ± 0.4) − (10 ± 0.2)/θ. Both these rate constants are pertinent to kinetic studies of the photoinduced addition of SF5C1 to olefins.

THE DECOMPOSITION OF SILYL PEROXIDES

1964 ◽  
Vol 42 (5) ◽  
pp. 985-989 ◽  
Author(s):  
Richard R. Hiatt
Keyword(s):  
Thermal Decomposition ◽  
Rate Constant ◽  
Half Life ◽  
Order Rate Constant ◽  
Butyl Alcohol ◽  
Base Catalysis ◽  
First Order ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Acid And Base

The thermal decomposition of tert-butyl trimethylsilyl peroxide has been investigated and found to be sensitive to acid and base catalysis and to the nature of the solvent. In heptane and iso-octane the first-order rate constant could be expressed as 1.09 × 1015e−41200/RT and in 1-octene as 3.90 × 1015e−41200/RT (sec−1). The half life at 203 °C was about 1 hour. The reaction was faster in aromatic solvents; in chlorobenzene it was complicated by formation of HCl from the solvent.Products of the reaction were acetone, tert-butyl alcohol and hexamethyldisiloxane.

Effect of ß-Carotene on Delayed Light Emission from Aggregated Chlorophyll

1990 ◽  
Vol 45 (1-2) ◽  
pp. 132-134 ◽  
Author(s):  
Shan-Yuan Yang ◽  
S. S. Brody
Keyword(s):  
Energy Transfer ◽  
Half Life ◽  
Light Emission ◽  
Order Process ◽  
Dark Chamber ◽  
Delayed Light Emission ◽  
First Order ◽  
Β Carotene

Abstract Delayed light emission (DLE) from aggregated chlorophyll is used to probe energy transfer between aggre­ gated chlorophyll and β-carotene. Preilluminated β-carotene when injected into a dark chamber containing aggregated chlorophyll, induces DLE from aggregated chlorophyll. If the dark chamber contains only monomeric chlorophyll, there is no DLE. The intensity of DLE is dependent on the time of illumination of β-carotene. The decay of energy stored by the carotene is not a first order process. The first half life is about 2 min, the next about 10 min

ABSOLUTE RATE CONSTANTS FOR HYDROCARBON AUTOXIDATION: III. α-METHYLSTYRENE, β-METHYLSTYRENE, AND INDENE

1966 ◽  
Vol 44 (10) ◽  
pp. 1113-1118 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Isotope Effect ◽  
Rate Constant ◽  
Rate Constants ◽  
Propagation Rate ◽  
Absolute Rate ◽  
Order Process ◽  
Deuterium Isotope Effect ◽  
First Order ◽  
Process Rate Constant ◽  
Propagation Rate Constant

Absolute rate constants for the copolymerization of α-methylstyrene and oxygen have been measured from 13 to 50 °C. The propagation and termination rate constants can be represented by[Formula: see text]Experiments with 2,6-di-t-butyl-4-methylphenol at 65 °C have shown that C6H5C(CH3):CH2 and C6H5C(CD3):CD2 have the same propagation rate constant but that chain termination involves a deuterium isotope effect (kt)H/(kt)D ≈ 1.5.Absolute rate constants for the copolymerization of oxygen with β-methylstyrene and with indene at 30 °C showed that a significant fraction of the oxidation chains were terminated by a kinetically first order process (rate constant kx). The rate constants for β-methylstyrene and indene at 30 °C are kp = 51 and 142 l mole−1 s−1, kt = 1.6 × 107 and 2.5 × 107 l mole−1 s−1, and kx = 0.61 and 1.2 s−1, respectively. The propagation rate constant for indene can be separated into a rate constant for the copolymerization with oxygen (kadd = 128 l mole−1 s−1) and a rate constant for hydrogen atom abstraction (kabstr = 14 l mole−1 s−1). In the presence of heavy water the first order process for indene had a deuterium isotope effect (kx)/(kx)D2O ≈ 3.

Darstellung und Thermolyse tert-butylsubstituierter Silatetrazoline – Erzeugung der Silanimine tBu2Si=N-SiXtBu2 (X = F, Cl, Br, tBu) Synthesis and Thermolysis of the tert-Butyl-Substituted Silatetrazolines – Formation of the Silanimines tBu2Si=N-SiXtBu2 (X = F, Cl, Br, tBu)

2002 ◽  
Vol 57 (11) ◽  
pp. 1199-1206 ◽  
Author(s):  
Hans-Wolfram Lerner ◽  
Nils Wiberg ◽  
K. Polborn
Keyword(s):  
Structure Analysis ◽  
Order Process ◽  
X Ray ◽  
First Order ◽  
Tert Butyl ◽  
Substituted 1

The silanimine tBu2Si=N-SitBu3 reacts with the silyl azides tBuMe2SiN3 or tBu2SiXN3 (X = H, Me, F, Cl, Br) to form the corresponding tert-butyl-substituted 1-tri-tert-butylsilyl-4-triorganosilyl- 5,5-di-tert-butylsilatetrazolines. The silatetrazolines with chloro-di-tert-butylsilyl and bromo-di-tert-butylsilyl substituents can also be synthesized by treating two equivalents of tBu2SiXN3 (X = Cl, Br) with the silanide tBu3SiNa. In the thermolysis of the silaterazolines the silanimines tBu2Si=N-SiXtBu2 (X = F, Cl, Br, tBu) and silyl azides are formed in a first-order process. The silanimines tBu2Si=N-SiXtBu2 (X= F, Cl, Br, tBu) have been trapped with acetone by en-reaction. The structure of (dimethyl-tert-butylsilyl)-substituted silatetrazoline has been determined by X-ray structure analysis.

scholarly journals Degradation kinetics of six sulfonamides in hen eggs under simulated cooking temperatures

2011 ◽  
Vol 76 (8) ◽  
pp. 1093-1101 ◽  
Author(s):  
Xin-Huai Zhao ◽  
Peng Wu ◽  
Ying-Hua Zhang
Keyword(s):  
Rate Constants ◽  
Half Life ◽  
Heating Temperature ◽  
Degradation Kinetics ◽  
Life Time ◽  
Hplc Method ◽  
First Order ◽  
Order Rate ◽  
Apparent Activation Energies ◽  
Kinetics Of

Six sulfonamides, i.e., sulfadiazine, sulfadimethoxine, sulfamerazine, sulfamethazine, sulfamethoxazole and sulfamonomethoxine, were applied to spike whole hen eggs at 0.1 mg kg- 1 eggs. The spiked hen eggs were heated at 80 and 100 ?C to investigate the degradation kinetics of the sulfonamides under simulated cooking conditions. The sulfonamides added were extracted twice from the spiked eggs with dichloromethane by an ultrasonic-assistant extraction, and analyzed by a HPLC method after purification. The first-order rate constants and half-life times of the sulfonamides were calculated, and the corresponding apparent activation energy of their degradation was also obtained by application of the Arrhenius equation. The results indicated that all six sulfonamides degraded faster at the higher heating temperature, with first-order rate constants ranging from 0.0056 to 0.0108 min-1 at 80 ?C and from 0.0147 to 0.0394 min-1 at 100 ?C. The apparent activation energies for the degradation of the sulfonamides were estimated to be in the range 30.9 to 77.5 kJ mol-1. Sulfadiazine and sulfadimethoxine had the shortest and longest half-life time, respectively, and were the most instable and stable.

Desorption rate of volatile compounds in polishing ponds

2011 ◽  
Vol 63 (6) ◽  
pp. 1177-1182
Author(s):  
Eudes M. Alves ◽  
Paula F. C. Cavalcanti ◽  
Adrianus van Haandel
Keyword(s):  
Carbon Dioxide ◽  
Experimental Investigation ◽  
Volatile Compounds ◽  
Rate Constants ◽  
Driving Force ◽  
Co2 Removal ◽  
Desorption Rate ◽  
Order Process ◽  
First Order ◽  
Co2 Desorption

Increase of pH in polishing ponds can be predicted quantitatively from variations in alkalinity and acidity. These variables are affected by processes that develop simultaneously in ponds: (1) CO2 desorption, (2) biological CO2 removal by photosynthesis and (3) NH3 desorption. An experimental investigation was carried out to determine the desorption rate of carbon dioxide and ammonium. It is shown that CO2 and NH3 desorption can be described by Fick’s law, which describes desorption of a gaseous compounds from water as a first order process with respect to the degree of oversaturation, which is the driving force of the process. An experimental investigation was carried out to determine the desorption rate constants. The value of the constant proved to be inversely proportional to the depth of the pond (H) and its value for H=1 m and at 26°C was established as KCO2=0.34/H d−1 for carbon dioxide and KNH3=0.33/H d−1 for ammonium.

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