scholarly journals STUDIES ON THE PERVANADIUM COMPLEX

1961 ◽  
Vol 39 (6) ◽  
pp. 1174-1183 ◽  
Author(s):  
G. A. Dean
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Acid Solution ◽  
Anionic Complex ◽  
Cationic Complex ◽  
Kcal Mole ◽  
Decomposition Products ◽  
First Order ◽  
Discrete Variations ◽  
Kinetics Of

The 'pervanadium complex' is investigated in a general manner. The kinetics of its thermal decomposition in acid solution are shown to be first order with respect to pervanadium, the apparent activation energy is 26.5 ± 1.0 kcal/mole, and possible mechanisms are suggested. The effect of various acids upon the nature of the decomposition products is determined: almost quantitative yields of vanadium (V) or vanadium (IV) are obtained in very dilute or concentrated acid, respectively. Spectrophotometric studies indicate that in acid solution two separate complexes exist: a red (1:1) cationic complex and a yellow (1:2) anionic complex. The stoichiometry of the equilibrium between the two complexes in solutions of sulphuric acid is investigated by a method of 'discrete variations'. The equilibrium could be described by[Formula: see text]where Kr/y = 2.2 ± 0.2 at 22 °C. The anion is shown to play an important part in determining the nature of the pervanadium complex.

scholarly journals The dissociation energy of the C-N bond in benzylamine

1949 ◽  
Vol 198 (1053) ◽  
pp. 285-292 ◽  
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Dissociation Energy ◽  
Heat Of Formation ◽  
Molar Ratio ◽  
Kcal Mole ◽  
First Order ◽  
First Order Kinetics ◽  
Permanent Gases ◽  
Kinetics Of

The kinetics of the thermal decomposition of benzylamine were studied by a flow method using toluene as a carrier gas. The decomposition produced NH 3 and dibenzyl in a molar ratio of 1:1, and small quantities of permanent gases consisting mainly of H 2 . Over a temperature range of 150° (650 to 800° C) the process was found to be a homogeneous gas reaction, following first-order kinetics, the rate constant being expressed by k = 6 x 10 12 exp (59,000/ RT ) sec. -1 . It was concluded, therefore, that the mechanism of the decomposition could be represented by the following equations: C 6 H 5 . CH 2 . NH 2 → C 6 H 5 . CH 2 • + NH 2 •, C 6 H 5 . CH 3 + NH 2 •→ C 6 H 5 . CH 2 • + NH 3 , 2C 6 H 5 . CH 2 •→ dibenzyl, and the experimentally determined activation energy of 59 ± 4 kcal./mole is equal to the dissociation energy of the C-N bond in benzylamine. Using the available thermochemical data we calculated on this basis the heat of formation of the NH 2 radical as 35.5 kcal./mole, in a fair agreement with the result obtained by the study of the pyrolysis of hydrazine. A review of the reactions of the NH 2 radicals is given.

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.

The thermal decomposition of RDX at temperatures below the melting point. II. Activation energy

1970 ◽  
Vol 23 (4) ◽  
pp. 749 ◽  
Author(s):  
JJ Batten ◽  
DC Murdie
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Melting Point ◽  
Kinetic Parameter ◽  
Arrhenius Equation ◽  
Kcal Mole ◽  
Decomposition Products ◽  
Sample Geometry ◽  
Temperature Range ◽  
Definition Of

The activation energy has been determined in the temperature range 170-198�. If the sample was spread the activation energy was independent of the definition of the kinetic parameter substituted in the Arrhenius equation and was 63 kcal mole-1. In the case of the unspread samples the activation energies of the induction, acceleration, and maximum rates were 49, 43, and 62 kcal mole-1 respectively. The effect that sample geometry has on the activation energy is attributed to gaseous decomposition products influencing the reaction.

FREE RADICALS BY MASS SPECTROMETRY: XXXV. THE HEAT OF FORMATION OF ALLYL RADICAL FROM BIALLYL PYROLYSIS

1966 ◽  
Vol 44 (18) ◽  
pp. 2211-2217 ◽  
Author(s):  
J. B. Homer ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Thermal Decomposition ◽  
Total Pressure ◽  
Heat Of Formation ◽  
Kcal Mole ◽  
Allyl Radical ◽  
First Order ◽  
Secondary Reactions ◽  
Gas Pressures

The thermal decomposition of biallyl has been investigated from 977 – 1 070 °K at helium carrier gas pressures of 10–50 Torr. Under these conditions the rate of central C—C bond fission to give two allyl radicals can be measured without interference from secondary reactions. The reaction at the pressures employed is first order with respect to biallyl, but between first and second order in the total pressure. The temperature dependence of the rate constants, extrapolated to infinite pressure, and corrected to 298 °K, gives an activation energy of 45.7 kcal/mole for the reaction, corresponding to ΔHf(allyl) = 33.0 kcal/mole.

THE NON-ENZYMATIC HYDROLYSIS OF ADENOSINE DIPHOSPHATE

1957 ◽  
Vol 35 (12) ◽  
pp. 1496-1503 ◽  
Author(s):  
K. A. Holbrook ◽  
Ludovic Ouellet
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Enzymatic Hydrolysis ◽  
Inorganic Phosphate ◽  
Adenosine Diphosphate ◽  
Hydrogen Ions ◽  
Kcal Mole ◽  
First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the non-enzymatic hydrolysis of adenosine diphosphate in aqueous solution have been studied at pH 3.5 to 10.5 and temperatures from 80° to 95 °C. The reaction has been followed by measuring colorimetrically the inorganic phosphate liberated according to the over-all reaction[Formula: see text]The reaction has been found to be first order with respect to ADP concentration and to be catalyzed by hydrogen ions. From rate studies at pH 8.0 an activation energy of 24.2 kcal./mole was derived. A mechanism is proposed to account for the observed facts and the mechanism for the hydrolysis of adenosine triphosphate is also discussed.

THE THERMAL DECOMPOSITION OF STYRENE–BUTADIENE POPCORN POLYMER

1950 ◽  
Vol 28b (1) ◽  
pp. 5-16
Author(s):  
C. A. Winkler ◽  
J. Halpern
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Linear Relation ◽  
Frequency Factor ◽  
Thermal Reaction ◽  
Cross Linking ◽  
First Order ◽  
Bond Scission ◽  
Styrene Butadiene ◽  
Kinetics Of

At temperatures of the order of 250 °C., popcorn polymer undergoes decomposition to soluble polymer. The reaction is catalyzed by peroxides present in the popcorn when the latter is formed. These peroxides may be removed by extracting the polymer with benzene. The kinetics of both the catalyzed and purely thermal solubilization reactions were investigated. The rates of both reactions are first order, the catalyzed degradation having a higher activation energy and a higher frequency factor. The rate of the thermal reaction decreases and its activation energy increases with increasing butadiene content of the polymer. A linear relation between the activation energy and the log of the frequency factor, for the decomposition of popcorn polymers of different butadiene contents, was observed. The results indicate that the rate of solubilization is determined by the activation energy of the bond scission process, and is independent of the degree of cross-linking of the polymer.

THE THERMAL DECOMPOSITION OF METHYL HYDROPEROXIDE

1965 ◽  
Vol 43 (8) ◽  
pp. 2236-2242 ◽  
Author(s):  
Alexander D. Kirk
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Rate Constants ◽  
Dimethyl Phthalate ◽  
Kcal Mole ◽  
First Order ◽  
Methyl Hydroperoxide ◽  
Expected Values ◽  
Homogeneous Decomposition

The thermal decomposition of methyl hydroperoxide has been studied in solution and in the gas phase. The decomposition was found to be partly heterogeneous in solution in dimethyl phthalate and no reliable rate constants were obtained. Use of the toluene carrier method for the gas phase work enabled measurement of the rate constant for the homogeneous decomposition. The first order rate constants obtained range from 0.19 s−1 at 292 °C to 1.5 s−1 at 378 °C, leading to log A, 11± 2, and activation energy, 32 ± 5 kcal/mole. These results are compared with the expected values of log A, 13–14, and activation energy, 42 kcal/mole. The significance of these findings is discussed.

THE NON-ENZYMATIC HYDROLYSIS OF p-NITROPHENYL PHOSPHATE

1958 ◽  
Vol 36 (4) ◽  
pp. 686-690 ◽  
Author(s):  
K. A. Holbrook ◽  
Ludovic Ouellet
Keyword(s):  
Activation Energy ◽  
Enzymatic Hydrolysis ◽  
Ionic Species ◽  
Kcal Mole ◽  
First Order ◽  
Colorimetric Measurement ◽  
Nitrophenyl Phosphate ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the non-enzymatic hydrolysis of p-nitrophenyl phosphate have been studied in aqueous solution in the pH range 2.6 to 9.0 and at temperatures from 68.0°to 82.0 °C. The reaction has been followed by colorimetric measurement of the nitrophenol produced by the reaction[Formula: see text]The reaction is first order with respect to p-nitrophenyl phosphate and has an activation energy of 26.0 kcal./mole at pH 2.6. An explanation has been proposed in terms of the different rates of hydrolysis of the various ionic species of the ester present in solution.

THE THERMAL DECOMPOSITION OF PHENYLACETIC ACID

1960 ◽  
Vol 38 (8) ◽  
pp. 1261-1270 ◽  
Author(s):  
Margaret H. Back ◽  
A. H. Sehon
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Rate Constant ◽  
Phenylacetic Acid ◽  
Order Process ◽  
First Order ◽  
Kinetics Of ◽  
Dissociation Step

The thermal decomposition of phenylacetic acid was investigated by the toluene-carrier technique over the temperature range 587 to 722 °C. The products of the pyrolysis were carbon dioxide, carbon monoxide, hydrogen, methane, dibenzyl, and phenylketene. From the kinetics of the decomposition it was concluded that the reaction[Formula: see text]was a homogeneous, first-order process and that the rate constant of this dissociation step was represented by the expression k = 8 × 1012.e−55,000/RT sec−1. The activation energy of this reaction may be identified with D(C6H5CH2—COOH). The possible reactions of carboxyl radicals are discussed.

Ethylene exchange in PtCl(C5H7O2)(π-C2H4)

1970 ◽  
Vol 48 (24) ◽  
pp. 3802-3806 ◽  
Author(s):  
C. E. Holloway ◽  
J. Fogelman
Keyword(s):  
Activation Energy ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Kcal Mole ◽  
First Order ◽  
First Order Kinetics ◽  
Solvent Dependence ◽  
Kinetics Of

The kinetics of exchange of free with complexed ethylene in the system PtCl(acac)(π-C2H4) have been investigated over a temperature and concentration range by proton magnetic resonance. First order kinetics are observed with respect to each component with no solvent dependence of rate. The activation energy and entropy are 2.7 kcal mole−1 and −36 cal deg−1 mole−1, respectively. A five coordinate intermediate is suggested, with complete retention of configuration at the platinum.

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