The Rate-Constant for the Recombination of Methyl Radicals

1986 ◽  
Vol 39 (8) ◽  
pp. 1257 ◽  
Author(s):  
NL Arthur ◽  
JC Biordi
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Rate Constant ◽  
Rate Constants ◽  
The Other ◽  
Methyl Radicals ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Best Value ◽  
Limiting Value

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.

Absolute Viscosity of Air down to Cryogenic Temperatures and up to High Pressures

1973 ◽  
Vol 15 (4) ◽  
pp. 266-270 ◽  
Author(s):  
B. Latto ◽  
M. W. Saunders
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Atmospheric Pressure ◽  
High Pressures ◽  
The Other ◽  
Cryogenic Temperatures ◽  
Temperature Range ◽  
Absolute Viscosity ◽  
Correlating Equations ◽  
Better Than

The absolute viscosity of gaseous air was determined experimentally for the general pressure and temperature range 100–15 000 kPa and 90–400 K respectively, using a series capillary transpiration-type viscometer which has been developed by the authors. The accuracy of the experimental data is believed to be better than ± 1 per cent. Two general correlating equations, one for atmospheric pressure and the other for medium high pressure (i.e., densities up to 400 kg/m3), have been obtained.

Reactions of methyl radicals. I. Hydrogen abstraction from dimethyl sulphide

1976 ◽  
Vol 29 (7) ◽  
pp. 1483 ◽  
Author(s):  
NL Arthur ◽  
M Lee
Keyword(s):  
Free Radicals ◽  
Rate Constant ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Reverse Reaction ◽  
Thermochemical Data ◽  
Methyl Radicals ◽  
Dimethyl Sulphide ◽  
Temperature Range

Hydrogen abstraction from (CH3),S and CH3COCH3 by CH3 radicals CH3+CH3SCH3 → CH4+CH3SCH2 CH3 + CH3COCH3 → CH4 + CH3COCH2 has been studied in the temperature range 120-245�. The rate constants, based on the value of 1013.34cm3 mol-l s-1 for the recombination of CH3 radicals, are given by (k in cm3 mol-1 s-1, E in kJ mol-1, R = 0.008314 kJ K-1 mol-1): logk1 = (11.62 � 0.08) ? (38.35 � 0.68)/2.303RT logk3 = (11.61 � 0.05) ? (40.48 � 0.46)/2.303RT Combination of the results for (1) with thermochemical data gives a calculated value of Logk-1 = (11.8 -63.7/2.303RT for the rate constant of the reverse reaction. The results for CH3+(CH3)2S are compared with all of the available data for hydrogen abstraction by free radicals from both sulphur-containing compounds, and molecules of the type (CH3)xM.

The homogeneous conversion of methane to higher hydrocarbons in the presence of ethylene in the temperature range 925–1023 K

1991 ◽  
Vol 69 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Alain R. Bossard ◽  
Margaret H. Back
Keyword(s):  
Hydrogen Abstraction ◽  
Homogeneous System ◽  
Catalytic Reactions ◽  
The Other ◽  
Methyl Radicals ◽  
Temperature Range ◽  
Vinyl Radicals ◽  
Conversion Of Methane ◽  
Radical Distribution ◽  
Higher Hydrocarbons

Mixtures of ethylene and methane have been pyrolyzed in the temperature range 925–1023 K for the purpose of converting methane to higher hydrocarbons. Addition of methane to thermally-reacting ethylene increases the rate of formation of propylene but decreases the rates of formation of the other major products, ethane, acetylene, and butadiene. Hydrogen abstraction from methane is a major propagation reaction and causes a shift in the radical distribution from ethyl and vinyl radicals, the main radicals in the pyrolysis reactions of ethylene alone, to methyl radicals, which lead to the formation of propylene. At 1023 K with a pressure of ethylene of 6.5 Torr and of methane of 356 Torr, 1.5 mol of methane is converted to higher molecular weight products for every mole of ethylene reacted. The rate of conversion of methane in the homogeneous system is lower than in catalytic reactions but the product is entirely hydrocarbon and no methane is lost to carbon monoxide or carbon dioxide. Key words: methane, ethylene, kinetics, pyrolysis, fuels.

Temperature dependence of the limiting low- and high-pressure rate constants for the CH3O+NO2+He reaction over the 250–390 K temperature range

2000 ◽  
Vol 329 (3-4) ◽  
pp. 191-199 ◽  
Author(s):  
E. Martı́nez ◽  
J. Albaladejo ◽  
E. Jiménez ◽  
A. Notario ◽  
Y. Dı́az de Mera
Keyword(s):  
High Pressure ◽  
Temperature Dependence ◽  
Rate Constants ◽  
Temperature Range

scholarly journals DYNAMICS OF NEUROMUSCULAR TRANSMISSION REPRODUCED BY CALCIUM-DEPENDENT SERIAL TRANSITIONS IN THE VESICLE FUSION COMPLEX

2021 ◽  
Author(s):  
Alejandro Martínez-Valencia ◽  
Guillermo Ramírez-Santiago ◽  
Francisco F. De-Miguel
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Electrical Activity ◽  
Rate Constant ◽  
Rate Constants ◽  
Resting State ◽  
Neuromuscular Transmission ◽  
Spontaneous Release ◽  
Calcium Dependent ◽  
Vesicle Pool

Neuromuscular transmission, from spontaneous release to facilitation and depression was accurately reproduced by a mechanistic kinetic model of sequential maturation transitions in the molecular fusion complex. The model incorporates three predictions. First, sequential calcium-dependent forward transitions take vesicles from docked to pre-primed to primed states, followed by fusion. Second, pre-priming and priming are reversible. Third, fusion and recycling are unidirectional. The model was fed with experimental data from previous studies while the backward (β) and recycling (ρ) rate constant values were fitted. Classical experiments were successfully reproduced when every forward (α) rate constant had the same value, and both backward rate constants were 50-100 times larger. Such disproportion originated an abruptly decreasing gradient of resting vesicles from docked to primed states. Simulations also predict that: i. Spontaneous release reflects primed to fusion spontaneous transitions. ii. Calcium elevations synchronize the series of forward transitions that lead to fusion. iii Facilitation reflects a transient increase of priming following calcium-dependent transitions. iv. Backward transitions and recycling restore the resting state. v. Depression reflects backward transitions and slow recycling after intense release. Such finely-tuned kinetics offers a mechanism for collective non-linear transitional adaptations of a homogeneous vesicle pool to an ever-changing pattern of electrical activity.

scholarly journals Predicting pressure-dependent unimolecular rate constants using variational transition state theory with multidimensional tunneling combined with system-specific quantum RRK theory: a definitive test for fluoroform dissociation

2016 ◽  
Vol 18 (25) ◽  
pp. 16659-16670 ◽  
Author(s):  
Junwei Lucas Bao ◽  
Xin Zhang ◽  
Donald G. Truhlar
Keyword(s):  
Experimental Data ◽  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Temperature Range ◽  
Multidimensional Tunneling ◽  
Specific Quantum ◽  
Wide Pressure

We show that rate constants for dissociation of fluoroform computed by VTST/SS-QRRK agree excellently with definitive experimental data over a wide pressure and temperature range.

Kinetics of renin-antirenin reaction: micromethods for the assay of renin and antirenin

1975 ◽  
Vol 228 (4) ◽  
pp. 973-979 ◽  
Author(s):  
E Haas ◽  
H Goldblatt ◽  
RL Klick ◽  
L Lewis
Keyword(s):  
Experimental Data ◽  
Lower Limit ◽  
Rate Constant ◽  
Rate Constants ◽  
Data Accuracy ◽  
Michaelis Constant ◽  
Renin Substrate ◽  
Method Of Calculation ◽  
Human Renin ◽  
Kinetics Of

Indirect micromethods were designed for the assay of human renin (lower limit 0.25 times 10-4 U and of antirenin to human renin (lower limit 3 times 10-4 U), with the rat used for the bioassay of the angiotensin produced by the action of renin on renin substrate. This made possible the assay of unusually small amounts (0.01 mu1) of serum for antirenin. The Michaelis-Menten concept of a dissociating complex can be applied to the antireninrenin reaction: the rate constants for the formation and for the breakdown of the complex were k1 equal to 1.65 (ml/U antirenin per min) and k3 equal to 1.97 times 10-3 (U inactivated renin/U antirenin per min), respectively; the apparent Michaelis constant was 12 times 10-4 (U renin/ml). A second method of analysis was also applied by assuming the formation of a rather tight complex, with antirenin functioning as an irreversible inactivator of renin. Both methods of analysis yielded practically the same rate constant (k1 equal to 1.65 and k1 equal to 1.71), but the treatment according to the Michaelis-Menten equation affords a slightly better fit of the experimental data (accuracy equal to plus or minus 15.5 percent) than the second method of calculation (accuracy equal to plus or minus 21.6 percent).

scholarly journals Rhodopsin photoproducts and rod sensitivity in the skate retina.

1977 ◽  
Vol 69 (1) ◽  
pp. 97-120 ◽  
Author(s):  
K P Brin ◽  
H Ripps
Keyword(s):  
Experimental Data ◽  
Computer Simulation ◽  
Rate Constants ◽  
Dark Adaptation ◽  
Photochemical Reactions ◽  
The Other ◽  
Thermal Reactions ◽  
Rate Of Recovery ◽  
Spectral Absorbance ◽  
Kinetics Of

The late photoproducts that result from the isomerization of rhodopsin have been identified in the isolated all-rod retina of the skate by means of rapid spectrophotometry. The sequence in which these intermediates form and decay could be described by a scheme that incorporates two pathways for the degradation of metarhodopsin II (MII) to retinol: one via metarhodopsin III (MIII) and the other (which bypasses MIII) through retinal. Computer simulation of the model yielded rate constants and spectral absorbance coefficients for the late photoproducts which fit experimental data obtained at temperatures ranging from 7 degrees C to 27 degrees C. Comparing the kinetics of the thermal reactions with the changes in rod threshold that occur during dark adaptation indicated that the decay of MII and the fall in receptor thresholds exhibit similarities with regard to their temperature dependence. However, the addition of 2 mM hydroxylamine to a perfusate bathing the retina greatly accelerated the photochemical reactions, but had no significant effect on the rate of recovery of rod sensitivity. It appears, therefore, that the late bleaching intermediates do not control the sensitivities of skate rods during dark adaptation.

Intramolekulare Excimere: Die Kinetik ihrer Bildung und Desaktivierung

1970 ◽  
Vol 25 (7) ◽  
pp. 1091-1096 ◽  
Author(s):  
Walter Klöpffer ◽  
Wolfgang Liptay
Keyword(s):  
Experimental Data ◽  
Rate Constant ◽  
Rate Constants ◽  
Kinetic Equations ◽  
High Rate ◽  
Excimer Fluorescence ◽  
Intramolecular Excimer ◽  
Excimer Formation

A set of kinetic equations has been developed which allows to calculate the rate parameters of intramolecular excimer formation, dissociation and of radiative and non-radiative desactivation processes. Experimental data necessary for evaluating the equations are monomer lifetime and relative fluorescence intensities of monomer and excimer fluorescence in solution with and without added quenching substance.Spectroscopical data of biscarbazolyl propane, diphenyl propane and derivatives are used in order to calculate the rate constants. It is shown that the stronger excimer fluorescence of diphenyl propane, as compared with biscarbazolyl propane, is due to the high rate constant of excimer formation in the former substance

Rate Constants for D + C2H2→ C2HD + H at High Temperature:  Implications to the High Pressure Rate Constant for H + C2H2→ C2H3†

2003 ◽  
Vol 107 (49) ◽  
pp. 10533-10543 ◽  
Author(s):  
J. V. Michael ◽  
M.-C. Su ◽  
J. W. Sutherland ◽  
L. B. Harding ◽  
A. F. Wagner
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Rate Constant ◽  
Rate Constants
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