A shock-tube study of the kinetics of decomposition of sulphur dioxide

1963 ◽  
Vol 276 (1367) ◽  
pp. 461-474 ◽  
Keyword(s):  
Activation Energy ◽  
Triplet State ◽  
Sulphur Dioxide ◽  
Direct Reaction ◽  
Kcal Mole ◽  
Absorption Bands ◽  
True Activation Energy ◽  
Rate Of Increase ◽  
Reaction Theory ◽  
Kinetics Of

The rate of increase in strength of absorption bands of SO has been measured in shock-heated mixtures of sulphur dioxide and argon. Arrhenius-type plots indicate a unimolecular first step of the order d [SO]/d t = k [SO 2 ] [ M ], where [SO], [SO 2 ] and [ M ] are concentrations of [SO], [SO 2 ] and total gas. The apparent activation energy at around 3500 °K is 56 kcal/mole. It is shown that on unimolecular reaction theory, if four harmonic modes of oscillation in the SO 2 molecules contribute to the energy available for transformation, the true activation energy is 74 kcal/mole. This agrees with the energy of excitation to a known triplet state of SO 2 , and on this basis it is suggested that the first steps in the decomposition are SO 2 + M = SO* 2 + M — 73.6 kcal/mole (1) and SO* 2 + SO 2 = SO 3 + SO + 25.6 kcal/mole. (2) Step (2) is spin-allowed, whereas the more direct reaction SO 2 + SO 2 = SO 3 + SO —48 kcal/ mole is spin-forbidden. This is an unusual type of decomposition mechanism and occurs because of the high dissociation energy of SO 2 , because the direct step of low-energy is spinforbidden, and because there is a favourably situated triplet state of the molecule.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

Insect blood-brain barrier: a radioisotope study of the kinetics of exchange of a liposoluble molecule (n-butanol)

1976 ◽  
Vol 64 (1) ◽  
pp. 119-130
Author(s):  
M. V. Thomas
Keyword(s):  
Activation Energy ◽  
Temperature Sensitivity ◽  
Nerve Cord ◽  
Previous Investigation ◽  
Time Course ◽  
Kcal Mole ◽  
Similar Time ◽  
Kinetics Of ◽  
Butanol Concentration ◽  
Good Agreement

About 90% of the butanol uptake by the cockroach abdominal nerve cord washed out with half-times of a few seconds, in good agreement with an electrophysiological estimate, and the temperature sensitivity suggested an activation energy of 3 Kcal mole-1. The remaining activity washed out far more slowly, with a similar time course to that observed in a previous investigation which had not detected the fast fraction. Its size was similar to the non-volatile uptake, and was considerably affected by the butanol concentration and incubation period. It apparently consisted of butanol metabolites, which could be detected by chromatography.

Kinetics of the addition of acids to olefins with and without boron fluoride catalysis

1967 ◽  
Vol 45 (1) ◽  
pp. 11-16 ◽  
Author(s):  
G. A. Latrèmouille ◽  
A. M. Eastham
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Apparent Activation Energy ◽  
Trifluoroacetic Acid ◽  
Similar Rate ◽  
Ethylene Dichloride ◽  
Kcal Mole ◽  
Rate Law ◽  
Boron Fluoride ◽  
Kinetics Of

Isobutene reacts readily with excess trifluoroacetic acid in ethylene dichloride solution at ordinary temperatures to give t-butyl trifluoroacetate. The rate of the reaction is given, within the range of the experiments, by the expression d[ester]/dt = k[acid]2[olefin], and the apparent activation energy is about 6 kcal/mole. The rate of addition is markedly dependent on the strength of the reacting acid and is drastically reduced in the presence of mildly basic materials, such as dioxane. The boron fluoride catalyzed addition of acetic acid to 2-butene can be considered to follow a similar rate law, i.e. d[ester]/dt = k[acid·BF3]2[olefin], but only if some assumptions are made about the position of the equilibrium [Formula: see text]since only the 1:1 complex is reactive.

Chemical Vapor Deposition of SiO2 from Ozone-Organosilane Mixtures near Atmospheric Pressure

1992 ◽  
Vol 282 ◽  
Author(s):  
K. V. Guinn ◽  
J. A. Mucha
Keyword(s):  
Activation Energy ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Atmospheric Pressure ◽  
Chemical Vapor ◽  
Zero Order ◽  
Kcal Mole ◽  
Consumption Ratio ◽  
Zero Order Kinetics ◽  
Kinetics Of

ABSTRACTThe kinetics of deposition of SiO2 by the reaction of tetramethylsilane (TMS) with ozone (O3) has been studied over the temperature range 180 – 380° C and compared with available data for the same process using tetraethoxysilane (TEOS). Both processes exhibit the same activation energy (17 kcal/mole) below 300 ° C which falls-off at higher temperatures due to transport limitations. Transition from first- to zero-order kinetics occurs with increasing concentrations of TMS and O3, which gives an overall O3/TMS consumption ratio of 10 at 258° C and5 at 325° C. TEOS is estimated to be 5 times more reactive than TMS above 300° C and over 10 times more reactive in the kinetically-limited regime below 300° C. Results suggest that O3-induced SiO2 deposition proceeds via surface reactions and is limited by heterogeneous decomposition of ozone.

THE INFRARED SPECTRUM AND THERMAL DECOMPOSITION OF HYDRAZINE PERCHLORATE HEMIHYDRATE

1966 ◽  
Vol 44 (20) ◽  
pp. 2435-2443 ◽  
Author(s):  
P. W. M. Jacobs ◽  
A. Russell-Jones
Keyword(s):  
Infrared Spectrum ◽  
Reaction Mechanisms ◽  
Low Temperatures ◽  
Room Temperature ◽  
Kcal Mole ◽  
Absorption Bands ◽  
Kinetics Of Decomposition ◽  
Salt Melts ◽  
Chemical Equation ◽  
Kinetics Of

The infrared spectrum of hydrazine perchlorate hemihydrate (HPH) has been determined and an assignment of the absorption bands made. Invacuo, HPH will partially dehydrate even at room temperature; when heated the remainder of the half-mole of water is lost at 61 °C. The dehydrated salt melts at 138 °C and decomposition ensues. The kinetics of decomposition may be followed in the temperature range 180–280 °C. The activation energy is 36.3 kcal/mole. At low temperatures the decomposition is represented by the chemical equation[Formula: see text]but when the temperature is high enough the rate of decomposition of the ammonium perchlorate formed becomes appreciable also. Possible reaction mechanisms are discussed.

scholarly journals Frequency Dependent Kinetics of the CW CO2 Laser Induced Reaction of CF3CF2Cl

1987 ◽  
Vol 7 (5-6) ◽  
pp. 271-277
Author(s):  
R. N. Zitter ◽  
D. F. Koster ◽  
N. Siddiqua
Keyword(s):  
Activation Energy ◽  
Absorption Band ◽  
Co2 Laser ◽  
Laser Frequency ◽  
Kcal Mole ◽  
Band Center ◽  
Laser Frequencies ◽  
Cw Co2 Laser ◽  
Kinetics Of ◽  
Induced Reaction

Kinetics of the decomposition of CF3CF2Cl at 50 torr by a cw CO2 laser have been studied over a range of laser frequencies extending 36 cm−1 below an absorption band center at 980 cm−1. At constant translational temperature, the change in the rate constant with laser frequency is a factor of 100, comparable to the effect previously observed in CF2ClCF2Cl. Arrhenius plots show an activation energy of 86.2 kcal/mole, independent of frequency.

Vulcanization of Elastomers. 40. Vulcanization of Natural Rubber and Synthetic Rubber with Sulfur in Presence of Sulfenamides. III

1965 ◽  
Vol 38 (1) ◽  
pp. 189-203 ◽  
Author(s):  
W. Scheele ◽  
J. Helberg
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Natural Rubber ◽  
Rate Constants ◽  
Sulfur Concentration ◽  
Kcal Mole ◽  
Synthetic Rubber ◽  
Chemical Constitution ◽  
Induction Times ◽  
Kinetics Of

Abstract Vulcanization of natural rubber with sulfur was studied in presence of six sulfenamides, to determine the effect of the chemical constitution of the sulfenamide on sulfur decrease and on crosslinking. The results can be condensed as follows: (1) The kinetics of sulfur disappearance is in every respect qualitatively independent of the chemical constitution of the sulfenamide. (2) For the sulfenamides investigated, the smallest and largest rate constants for sulfur decrease differed only by a factor of two. (3) Greater differences are encountered in the induction times for sulfur decrease and for crosslinking. The latter are notably longer than those for sulfur disappearance. (4) The same activation energy, 23 kcal/mole, is derived from the temperature dependence of the induction times for all the sulfenamides. (5) The dissociation of sulfenamides in solution and their reaction with mercaptobenzothiazole were investigated further. The results provide the basis for a proposed reaction mechanism, which is presented in detail and can account for a number of the features typical of sulfenamide-accelerated vulcanization. (6) The drop in sulfur concentration goes at practically the same rate, if one introduces, instead of N, N-dicyclohexyl-2-benzothiazolesulfenamide, the corresponding ammonium mercaptide in equimolar concentration.

THE REACTION BETWEEN CYANATE AND HYPOCHLORITE

1956 ◽  
Vol 34 (4) ◽  
pp. 489-501 ◽  
Author(s):  
M. W. Lister
Keyword(s):  
Activation Energy ◽  
Ionic Strength ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Effect Of Temperature ◽  
Slow Step ◽  
True Activation Energy ◽  
Rate Of Reaction ◽  
Different Temperatures ◽  
Kinetics Of

The reaction between sodium hypochlorite and potassium cyanate in the presence of sodium hydroxide has been examined. The main products are chloride, and carbonate ions and nitrogen; but, especially if much hypochlorite is present, some nitrate is formed as well. The rate of reaction is proportional to the cyanate and hypochlorite concentrations, but inversely proportional to the hydroxide concentration: the rate constant is 5.45 × 10−4 min.−1 at 65 °C, at an ionic strength of 2.2. The rate constant increases somewhat as the ionic strength rises from 1.7 to 3.5. The effect of temperature makes the apparent activation energy 25 kcal./gm-molecule. The kinetics of the reaction suggest that the slow step is really a reaction of hypochlorous acid and cyanate ions, and possible intermediate products of this reaction are suggested. Allowing for the different extent of hydrolysis of hypochlorite at different temperatures, the true activation energy is found to be 15 kcal./gm-mol., which is consistent with the observed rate of reaction.

Spreading Kinetics of Molten 60Sn40Pb on Higher Melting Temperature Pb-Sn Alloy Substrates

1995 ◽  
Vol 390 ◽  
Author(s):  
H. Conrad ◽  
Z. Guo ◽  
D. Y. Jung
Keyword(s):  
Activation Energy ◽  
Contact Angle ◽  
Melting Point ◽  
Kcal Mole ◽  
Depth Of Penetration ◽  
Spherical Cap ◽  
Solid Diffusion ◽  
Time Exponent ◽  
Image Position ◽  
Kinetics Of

ABSTRACTThe spreading of molten 60Sn40Pb drops on higher melting point Pb-Sn alloy substrates (3 to 10 wt.% Sn) was investigated for reflow temperatures of 205° to 300°C. Following melting the drop assumed the form of a slightly flared, spherical cap with some penetration into the substrate beneath the contact area. The effects of time and temperature on the contact angle θ and the depth of penetration h were of the formwhere the apparent activation energy Q was 4.2 kcal/mole for θ and 16 kcal/mole for h. The time exponent m (negative for θ and positive for h) decreased with temperature from ∼ 0.2–0.3 at 205°C to ∼0.05 at 260° and then increased again at higher temperatures. The magnitude of Q for θ is in accord with that for the viscosity of molten Pb-Sn alloys and that for h with a combined liquid-solid diffusion involved in the dissolution. Further work is however needed to identify unequivocally the mechanisms which govern the wetting in these duplex Pb-Sn alloy systems.

Gas phase photochlorination of perfluorocyclohexene

1969 ◽  
Vol 47 (6) ◽  
pp. 1067-1069 ◽  
Author(s):  
J. J. Cosa ◽  
C. A. Vallana ◽  
E. H. Staricco
Keyword(s):  
Activation Energy ◽  
Quantum Yield ◽  
Gas Phase ◽  
Photochemical Reaction ◽  
Total Pressure ◽  
Square Root ◽  
Kcal Mole ◽  
Kinetics Of

The kinetics of the gas phase photochemical reaction between perfluorocyclohexene and chlorine was studied between 10 and 50 °C. The system was irradiated with light of 4360 Å. The rate of the photochlorination was independent of the perfluorocyclohexene pressure and of the total pressure. It was found to be proportional to the first power of the pressure of Cl2 and to the square root of the intensity of absorbed light. At 30 °C, the quantum yield was found to be 200 when the initial Cl2 pressure was 100 Torr, and intensity of light absorbed 9.89 × 10−9 einstein l−1s−1.An activation energy of 5.1 kcal/mole could be assigned to the reaction C6F10Cl + Cl2.

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