scholarly journals KINETICS OF THE REACTIONS BETWEEN ISOPROPYL CUMENE AND TERTIARY BUTYL CUMENE HYDROPEROXIDES AND IRON(II) IN DILUTE AQUEOUS SOLUTIONS IN THE ABSENCE OF OXYGEN

1952 ◽  
Vol 30 (12) ◽  
pp. 985-993 ◽  
Author(s):  
R. J. Orr ◽  
H. Leverne Williams
Keyword(s):  
Free Radicals ◽  
Rate Constants ◽  
Arrhenius Equation ◽  
Cumene Hydroperoxide ◽  
Bimolecular Reaction ◽  
Probable Error ◽  
Tertiary Butyl ◽  
Rate Of Reaction ◽  
Dilute Aqueous Solutions ◽  
Kinetics Of

From studies of the rate of reaction at 11°, 15°, 20°, and 26 °C. it was deduced that the bimolecular reaction between iron(II) and isopropyl cumene hydroperoxide is represented by[Formula: see text]At 0 °C. the radical induced oxidation of iron(II) due to inability of the monomer to remove the free radicals became appreciable. Addition of up to 7.5% methanol did not change the rate appreciably. The effect of traces of oxygen was negligible. Rate constants were measured at 15°, 9°, and 0 °C. for the reaction between iron(II) and the tertiary butyl cumene hydroperoxide. The average probable error in the determinations was 5.4%. From the data, the Arrhenius equation was determined as[Formula: see text]Comparison of the equations measured for cumene hydroperoxide, isopropyl cumene hydroperoxide, and tertiary butyl cumene hydroperoxide and iron(II) has been made. Changes in the constants have been explained qualitatively. The iodometric method of analysis when applied to tertiary butyl cumene hydroperoxide must be modified for accurate results. It is believed that the heating necessary in the presence of water decomposes the hydroperoxide.

Kinetics and Mechanisms of the Acid-catalysed Hydrolysis of Tertiary Butyl Acetate

1962 ◽  
Vol 15 (3) ◽  
pp. 467 ◽  
Author(s):  
KR Adam ◽  
I Lauder ◽  
VR Stimson
Keyword(s):  
Rate Constants ◽  
Butyl Acetate ◽  
Arrhenius Equation ◽  
Aqueous Acetone ◽  
Energy Of Activation ◽  
Kcal Mole ◽  
Tertiary Butyl ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the acid-catalysed hydrolysis of tertiary butyl acetate in water, in aqueous acetone, and in aqueous dioxan, over a range of temperature have been studied. The Arrhenius equation is not obeyed. In 40% water-60% acetone the energy of activation varies from 26-29 kcal mole-1 for temperatures 48-97 �C. This is due presumably to simultaneous hydrolyses via the AAL1 and the AAC2 mechanisms. By combination of oxygen-18 tracer results and kinetic results the rate constants for reactions by these mechanisms in water have been separated. The observed percentage of alkyl-oxygen fission in water varies from 85 at 25 �C to 97 at 60 �C. Rate constants for reactions by the AAL1 and the AAC2 mechanisms are expressed by the equations : k (sec-1 l mole-1) = 10l6.l exp (-27500/RT), and k (sec-1 l mole-1) = 107.9 exp (-l73OO/RT),respectively. However, the parameters of the latter equation may contain considerable errors because the extent of reaction by the AAC2 mechanism is small. In water and in 80% water-20% acetone, tertiary butyl acetate undergoes an uncatalysed solvolytic reaction, involving presumably the BAL1 mechanism. The variation of the rate of this reaction with temperature is expressed by the equation, k (sec-1) = 1012.3 exp (-26800/RT).

Kinetics of Mesophase Sphere Formation of Toluene Soluble Fraction

2013 ◽  
Vol 750-752 ◽  
pp. 1855-1859 ◽  
Author(s):  
Li Yue ◽  
Xue Fei Zhao ◽  
Shi Quan Lai ◽  
Xiao Xia Li ◽  
Liang Liang Gao ◽  
...  
Keyword(s):  
Rate Constants ◽  
Arrhenius Equation ◽  
Treatment Time ◽  
Soluble Fraction ◽  
Coal Tar ◽  
Treatment Temperature ◽  
Thermal Treatments ◽  
Exponential Factor ◽  
Sphere Formation ◽  
Kinetics Of

The toluene soluble (TS) fraction prepared from a middle-temperature coal tar pitch was subjected to a series of thermal treatments at the various temperatures from 410 °C to 470 °C for different periods of time. The samples obtained after heat treatment was quenched to ambient temperature. Mesophase spheres were separated from the quenched samples using washing oil and quinoline. The kinetics of mesophase sphere formation of the TS fraction was studied, based on the data derived from the time-dependent changes in the mesophase sphere content. It was clarified that the mesophase sphere formation of TS fraction was an autocatalytic type reaction. The rate law and the rate constants for the mesophase sphere formation at holding temperatures of 410°C, 430°C, 450°C and 470°C were determined. The rate constants of the mesophase sphere formation follow the Arrhenius equation. The Arrhenius parameters of the mesophase sphere formation are 200.2 kJ mol-1 of the activation energy and 2.71x1012 % -1 h-1 of the pre-exponential factor. The treatment temperature had a greater effect on the formation of mesophase spheres than the treatment time.

scholarly journals Formation of peroxides in amino acids and proteins exposed to oxygen free radicals

1993 ◽  
Vol 289 (3) ◽  
pp. 743-749 ◽  
Author(s):  
S Gebicki ◽  
J M Gebicki
Keyword(s):  
Amino Acids ◽  
Free Radicals ◽  
Oxygen Free Radicals ◽  
Radiation Energy ◽  
Protonated Form ◽  
Isoleucine Leucine ◽  
Protein Peroxidation ◽  
Dilute Aqueous Solutions ◽  
Kinetics Of

Dilute aqueous solutions of BSA or lysozyme gave positive tests for peroxides after exposure to reactive oxygen species. The reactive species were generated by gamma-irradiation, reduction of H2O2 with Fe2+ ions or thermal decomposition of an azo compound. Peroxides were assayed by an iodometric method. Identification of the new groups as hydroperoxides was confirmed by their ability to oxidize a range of compounds and by the kinetics of their reaction with iodide. The hydroperoxide groups were bound to the proteins and their yields (G values) corresponded to 1.2 -OOH groups per 100 eV of radiation energy absorbed for BSA, and 0.8 for lysozyme. The oxygen free radicals effective in protein peroxidation were the hydroxyl and organic peroxyl, but not superoxide or its protonated form. The efficiency of BSA peroxidation initiated by the hydroxyl radicals was 40%. Protein peroxides decayed spontaneously with a half-life of about 1.5 days at 20 degrees C. Exposure of the common amino acids to hydroxyl free radicals showed that six of them (glutamate, isoleucine, leucine, lysine, proline and valine) were peroxidized with similar efficiency to the proteins, whereas the rest were inert or much less susceptible. These results suggest that some proteins may be peroxidized by a variety of agents in vivo and that their subsequent reactions with protective agents, such as ascorbate or glutathione, may decrease the antioxidant potential of cells and tissues.

Kinetics of reactions between neutral free radicals. Rate constants for the reaction of CH radicals with N atoms between 216 and 584 K

1996 ◽  
Vol 92 (5) ◽  
pp. 723 ◽  
Author(s):  
Richard A. Brownsword ◽  
Simon D. Gatenby ◽  
Lee B. Herbert ◽  
Ian W. M. Smith ◽  
David W. A. Stewart ◽  
...  
Keyword(s):  
Free Radicals ◽  
Rate Constants ◽  
Kinetics Of

The kinetics of the reactions of sheep haemoglobin with iso cyanides

1960 ◽  
Vol 152 (948) ◽  
pp. 331-345 ◽  
Keyword(s):  
Chain Length ◽  
Steric Hindrance ◽  
Rate Constants ◽  
Homologous Series ◽  
Experimental Error ◽  
Initial Rate ◽  
The Other ◽  
Tertiary Butyl ◽  
Kinetics Of ◽  
Haemoglobin Molecule

The kinetic basis for the decrease in affinity of haemoglobin and myoglobin for successive members of the series of alkyl iso cyanides has been investigated. The initial rate of combination of ethyl, n -propyl, iso propyl, iso butyl and tertiary butyl iso cyanides with haemoglobin and with myoglobin decreases with increasing chain-length by about 500-fold in the case of haemoglobin and about 40-fold in the case of myoglobin. The rate of combination of the fourth iso cyanide molecule with haemoglobin (i. e. I + Hb 4 I 3 → Hb 4 I 4 ) is, however, only about 14 times smaller for tertiary butyl as compared with ethyl iso­ cyanide; this finding is in line with Pauling’s suggestion that combination of successive ligand molecules with haemoglobin decreases the steric hindrance for combination with further ligand molecules. The latter effect, however, varies considerably from ligand to ligand and is not only a property of the haemoglobin molecule. The velocity of dissociation of the first molecule of iso cyanide from saturated haemoglobin, on the other hand, is the same within experimental error for all members of the series. With myoglobin the rate constants for dissociation show differences of two- to three-fold, but there is no systematic trend. Thus the burden of accounting for the differences in affinity between the iso cyanides falls upon the combination velocity constants. This finding is in contrast to that for the gaseous ligands O 2 , CO and NO, where the affinity is primarily determined by the dissociation velocity constants. The bearing of the results on the ‘crevice’ hypothesis of haemoglobin structure is discussed. In line with the well-known fact that the first member of an homologous series is often anomalous it was found that the rate of dissociation of methyl iso cyanide from haemoglobin was about 50 times greater than that for all the higher homologues of the series. Preliminary experiments were carried out on the rate of combination of free haem with several of the iso cyanides, but were not pursued further on account of the difficulties mentioned in the text.

scholarly journals Effect of temperature and pH on carbamoylation and phosphorylation of serum cholinesterases. Theoretical interpretation of activation energies in complex reactions

1972 ◽  
Vol 130 (2) ◽  
pp. 515-524 ◽  
Author(s):  
V. Simeon ◽  
E. Reiner ◽  
C. A. Vernon
Keyword(s):  
Human Serum ◽  
Rate Constants ◽  
Time Course ◽  
Organophosphorus Compounds ◽  
Horse Serum ◽  
Bimolecular Reaction ◽  
Effect Of Temperature ◽  
Theoretical Interpretation ◽  
Serum Cholinesterase ◽  
Kinetics Of

1. The effect of temperature and pH was studied on the kinetics of inhibition of horse serum and human serum cholinesterase by four organophosphorus compounds and five carbamates. 2. For all compounds, and at each pH and temperature, the inhibition followed the kinetics of a bimolecular reaction with the inhibitor in excess, and with a negligible concentration of the Michaelis complex. 3. The second-order rate constants (ka) for inhibition of human serum cholinesterase by one organophosphate and one carbamate increased from 5° to 40°C with an apparent activation energy of 46kJ/mol (11kcal/mol). 4. The ka constant for inhibition of horse serum cholinesterase increased with temperature from 5° to 30°C, and then decreased from 30° to 40°C. The theoretical interpretation of such an unusual effect of temperature is derived. 5. The increase of ka with pH (human serum cholinesterase) followed the dissociation curve for a single group on the enzyme (pK7.5). 6. Rate constants for decarbamoylation (k+3) were determined, and the time-course of inhibition was calculated from the ka and k+3 constants.

Reactions of free radicals with aromatic compounds in the gaseous phase. III. Kinetics of the reaction of methyl radicals with anisole (methoxybenzene)

1967 ◽  
Vol 20 (6) ◽  
pp. 1155 ◽  
Author(s):  
MFR Mulcahy ◽  
BG Tucker ◽  
DJ Williams ◽  
JR Wilmshurst
Keyword(s):  
Free Radicals ◽  
Gaseous Phase ◽  
Aromatic Compounds ◽  
Phase Iii ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Rate Of Reaction ◽  
Reaction Proceeds ◽  
Kinetics Of Reaction ◽  
Kinetics Of

The kinetics of the reaction between methyl radicals and anisole have been studied at temperatures between 453 and 539�K and total pressures between 10 and 30 torr. The concentrations of methyl radicals ranged from 2 x 10-12 to 5 x 10-11 mole and those of anisole from 10-7 to mole cm-3. The reaction proceeds mainly by the mechanism ������������������ C6H5OCH3+CH3· → C6H5OCH2·+CH4���������������� (1)����������������� C6H5OCH2·+CH3· → C6H5OC2H5�������������������� (2)���������������� ���������C6H5OCH2· → C6H5CHO+H·������������������ (3) At 487�K attack on the aromatic ring to yield methyl anisoles is about twelve times slower than reaction (1). The Arrhenius parameters for reactions (1) and (8) are: log10(A1 cm3 mole-1 sec-1) = 11.7 � 0.3, and E1 = 10.5 � 0.8 kcal mole-1; log10(A8 sec-1) = 12.5, and E8 = 21 kcal mole-1. The last two values are based on the assumption that the kinetics of reaction (2) are similar to those of the recombination of methyl radicals. The rate of reaction (1) is about half that of the corre- sponding reaction with toluene and about five times that of the reaction with ethane in the above temperature range.

Simple Modification Measurement of Photodegradability of Polymers by using Photo-induced Chemiluminescence Technique

2013 ◽  
Vol 10 (2) ◽  
pp. 51
Author(s):  
Siti Farhana Zakaria ◽  
Keith R Millington
Keyword(s):  
Free Radicals ◽  
Organic Materials ◽  
Oxidative Degradation ◽  
Working Life ◽  
Bimolecular Reaction ◽  
Synthetic Polymers ◽  
Accelerated Weathering ◽  
Simple Modification ◽  
Uv Absorbers ◽  
Irradiation Period

Polymers and organic materials that are exposed to sunlight undergo photooxidation, which leads to deterioration of their physical properties. To allow adequate performance under outdoor conditions, synthetic polymers require additives such as antioxidants and UV absorbers. A major problem with optimising polymer formulations to maximise their working life span is that accelerated weathering tests are empirical. The conditions differ significantly from real weathering situations, and samples require lengthy irradiation period. Degradation may not be apparent in the early stages of exposure, although this is when products such as hydroperoxides are formed which later cause acceleration of oxidation. A simple way of quantifying the number of free radicals presents in organic materials following exposure to light or heat is by measuring chemiluminescence (CL) emission. Most polymers emit CL when they undergo oxidative degradation, and it originates from the bimolecular reaction of macroperoxy radicals which creates an excited carbonyl.

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 (< 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.

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