THE KINETICS OF THE PYROLYSIS OF TOLUENE

1954 ◽  
Vol 32 (3) ◽  
pp. 298-311 ◽  
Author(s):  
H. Blades ◽  
A. T. Blades ◽  
E. W. R. Steacie
Keyword(s):  
Rate Constants ◽  
Contact Time ◽  
First Order ◽  
Order Rate ◽  
Kinetics Of

The pyrolysis of toluene has been studied in an attempt to verify the findings of Szwarc (2). The major products have been confirmed but styrene and isomeric dimethyl diphenyls have also been detected. First order rate constants for the decomposition have been found to depend on the condition of the surface of the reactor, the contact time, and, to a lesser degree, on the pressure. Some preliminary studies on the mechanism of the formation of the dimethyl diphenyls are also recorded.

scholarly journals Compounds of 6, 13-Diamino-6, 13-Dimethyl-1, 4, 8, 11 - Tetraazacyclotetradecane

2021 ◽  
Author(s):  
◽  
Asokamali Siriwardena
Keyword(s):  
Rate Constants ◽  
Magnetic Measurements ◽  
Order Rate Constant ◽  
Acidic Solutions ◽  
First Order ◽  
Order Rate ◽  
Pendant Arm ◽  
Nickel Copper ◽  
13C Nuclear Magnetic Resonance ◽  
Kinetics Of

<p>The reaction of bis-(diaminoethane)nickel(II) chloride, ([Ni(en)2]Cl2 in methanol with formaldehyde and nitroethane in the presence of triethylamine proceeds readily to produce (6, 13-dimethyl-6, 13-dinitro-1, 4, 8, 11-tetraazacyclotetradecane)nickel(II) chloride, [Ni(dini)] - Cl2. Reduction of the nitro groups of this compound by catalytic hydrogenation yields three isomers of the pendant arm macrocyclic complex (6, 13-diamino-6, 13-dimethyl-1, 4, 8, 11-tetraazachyclotetradecane)nickel(II) chloride, designated a-, b- and c-[Ni(diam)]Cl2. These were separated by fractional crystallization. The aisomer was observed to isomerizes slowly in solution to the b- form. A parallel dissociation reaction of the a- isomer was also observed. The demetallation of a- and b- isomers of the diam complex of nickel by reaction with cyanide or concentrated acid at 140 degrees C produces the macrocycle meso-(6, 13-diamino-6, 13-dimethyl-1, 4, 8, 11-tetraazacyclotetra-decane), diam. A variety of hexamine, pentamine and tetramine complexes of diam with nickel(II), copper(II), cobalt(II) and (III), chromium(III), palladium(II), rhodium(III), zinc(II) and cadmium(II) were prepared. Hexamine and tetramine forms of labile metal complexes could be rapidly and reversibly interconverted by altering the pH. The hexamine cobalt(III) cation, [Co(diam)]3+ was by far the most inert of the prepared cobalt(III) complexes, remaining unaffected in hot acidic solutions. In contrast, a single pendant arm of the hexamine [Cr(diam)]3+ cation could be dissociated in acid. (Two possibly triamine complexes of lead were also prepared). These compounds were characterized by elemental analysis, magnetic measurements, electronic, infrared, 1H and 13C nuclear magnetic resonance spectra. The pendant arm protonation constants (log K) of diam and selected complexes of nickel, copper and palladium were calculated from potentiometric titration measurements at 25 degrees C. The log K values for diam at 25 degrees C (I = 0.1 M NaclO4) were 11.15, 9.7, 6.2 and 5.3. Kinetics of the parallel isomerization and dissociation of a-[Ni(dimH2)]4+ in HCl/NaCl solutions were monitored spectrophotometrically at 50 degrees C. The rate of reaction in acidic solutions showed a non-linear dependency on acid concentration. The observed first order rate constant (kobs) for disappearance of a-[Ni(diamH2)]4+ (by isomerization and dissociation) in 2.0 M HCl, 0.1 M NaOH and 2.0 M NaCl were 3.05 x 10-4, 2.0(3) x 10-2 and 5.0 x 10-5 s-1 respectively. The rate of the dissociation component of the reaction of a-[Ni(diamH2)]4+ in 2.0 M HCl at 50 degrees C was 1.82 x 10-7 s-1. Acid bydrolysis kinetics of (Cu[diamH2])(ClO4)4 in hydrochloric acid and perchloric acid at 50 and 70 degrees C were studied spectrophotometrically. The reactions were slow and the observed first order rate constants were to a first approximation independent of the particular acid or its concentration. The observed first order rate constants were 1 x 10-9 and 8 x 10-9 s-1 at 50 and 70 degrees C respectively. Questions about the nature of the reaction being followed have been raised.</p>

Degradation of propoxycarbazone-sodium with advanced oxidation processes

2011 ◽  
Vol 11 (1) ◽  
pp. 129-134 ◽  
Author(s):  
A. Dulov ◽  
N. Dulova ◽  
Y. Veressinina ◽  
M. Trapido
Keyword(s):  
Rate Constants ◽  
Advanced Oxidation Processes ◽  
Advanced Oxidation ◽  
Fenton Process ◽  
Oxidation Processes ◽  
First Order ◽  
Order Rate ◽  
Conversion Time ◽  
Pseudo First Order ◽  
Kinetics Of

The degradation of propoxycarbazone-sodium, an active component of commercial herbicide, in aqueous solution with ozone, UV photolysis and advanced oxidation processes: O3/UV, O3/UV/H2O2, H2O2/UV, and the Fenton process was studied. All these methods of degradation proved feasible. The kinetics of propoxycarbazone-sodium degradation in water followed the pseudo-first order equation for all studied processes except the Fenton treatment. The application of schemes with ozone demonstrated low pseudo-first order rate constants within the range of 10−4 s−1. Addition of UV radiation to the processes improved the removal of propoxycarbazone-sodium and increased the pseudo-first order rate constants to 10−3 s−1. The Fenton process was the most efficient and resulted in 5 and 60 s of half-life and 90% conversion time of propoxycarbazone-sodium, respectively, at 14 mM H2O2 concentration. UV treatment and the Fenton process may be recommended for practical application in decontamination of water or wastewater.

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: II. ISOBUTANE

1938 ◽  
Vol 16b (8) ◽  
pp. 260-272 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Rate Constants ◽  
Pressure Range ◽  
Reaction Rate ◽  
High Pressures ◽  
Initial Pressure ◽  
First Order ◽  
Decomposition Reactions ◽  
Order Rate ◽  
Reaction Proceeds ◽  
Kinetics Of

The kinetics of the thermal decomposition of isobutane has been investigated over an initial pressure range of from 5 to 60 cm., and at temperatures from 522 to 582 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in general agreement with those obtained by previous investigators. The reaction rate falls off with diminishing pressure, and the first order rate constants in a given run diminish strongly as the reaction proceeds. This behavior is similar to that of n-butane.Analyses of the products of the reaction were made at various stages, temperatures, and initial pressures by low-temperature distillation in a still of the Podbielniak type. The initial products were found by extrapolation to be H2, 35; CH4, 14; C2H4, 0.9; C2H6, 0.9; C3H6, 14; and C4H8, 35%. The results are compared with those of other workers.

THE KINETICS OF THE THERMAL DECOMPOSITION OF ETHYL BROMIDE AND ETHYL BROMIDE-d5

1958 ◽  
Vol 36 (7) ◽  
pp. 1043-1048 ◽  
Author(s):  
Arthur T. Blades
Keyword(s):  
Thermal Decomposition ◽  
Rate Constants ◽  
Pressure Effect ◽  
Ethyl Bromide ◽  
Carrier Gas ◽  
First Order ◽  
Order Rate ◽  
Kinetics Of

The kinetics of the pyrolysis of ethyl bromide and ethyl bromide-d5 have been studied using the toluene carrier gas technique. Variation of the pressure in the range 0.6 to 4.4 cm. Hg reveals what is believed to be a legitimate pressure effect on the first-order rate constants. The Arrhenius rate expressions determined at 4 cm. Hg pressure are: k(ethyl bromide) = 8.5 ± 1.6 × 1012e−52,200±300/RTsec−1 (T = 523°–633 °C);k(ethyl bromide-d5) = 2.1 ± 0.4 × 1013e−54,840±300/RT sec−1 (T = 531°–635 °C).The differences in the two rate expressions are discussed.

Some observations on the kinetics of the Jaffé reaction for creatinine.

1977 ◽  
Vol 23 (9) ◽  
pp. 1527-1530 ◽  
Author(s):  
R M Shoucri ◽  
M Pouliot
Keyword(s):  
Rate Constants ◽  
Kinetic Data ◽  
Serum Samples ◽  
First Order ◽  
Order Rate ◽  
First Order Kinetics ◽  
Pseudo First Order ◽  
Kinetics Of

Abstract The Jaffé reaction for creatinine assay appears to follow pseudo-first-order kinetics; first-order rate constants are different for different samples. Rate constants for 10 different serum samples varied from a low value of 0.0040 +/- 0.0003 s-1 to 0.0084 +/- 0.0008 s-1. We describe an approach for determining first-order rate constants from kinetic data and discuss the effects of the above observations on the mathematical formulations required for reliable kinetic determinations of creatinine.

THE PYROLYSIS OF TOLUENE

1962 ◽  
Vol 40 (7) ◽  
pp. 1310-1317 ◽  
Author(s):  
S. J. Price
Keyword(s):  
Activation Energy ◽  
Rate Constant ◽  
Rate Constants ◽  
Contact Time ◽  
Flow System ◽  
Kcal Mole ◽  
Homogeneous Process ◽  
First Order ◽  
Order Rate ◽  
Toluene Concentration

The pyrolysis of toluene has been studied in a flow system from 913 to 1143 °K. First-order rate constants are independent of the toluene concentration but decrease approximately 9% when the contact time is reduced from 1.0 to 0.41 second. Increasing the contact time from 1.0 second to 2.07 seconds does not affect the rate constant. The overall rate has been resolved into homogeneous and heterogeneous components. It is suggested that the activation energy of the homogeneous process, 85 kcal/mole, may be associated with D(C6H5CH2—H).

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: III. PROPANE

1938 ◽  
Vol 16b (11) ◽  
pp. 411-419 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Thermal Decomposition ◽  
High Pressure ◽  
Excellent Agreement ◽  
Rate Constants ◽  
Initial Pressure ◽  
First Order ◽  
Decomposition Reactions ◽  
Order Rate ◽  
Products Of Reaction ◽  
Kinetics Of

The kinetics of the thermal decomposition of propane has been investigated over a temperature range from 551° to 602 °C. The limiting high pressure first order rate constants are given by[Formula: see text]The first order rate constants fall off strongly with increasing percentage decomposition, and the rate decreases with decreasing pressure in a manner similar to the rate decrease in the decomposition of the butanes.Analyses of the products of reaction at various stages show them to be independent of temperature over the range examined, but to be affected by the initial pressure. This effect is undoubtedly due to the secondary hydrogenation of some of the initial products. The analytical results are in excellent agreement with those of Frey and Hepp.

scholarly journals Compounds of 6, 13-Diamino-6, 13-Dimethyl-1, 4, 8, 11 - Tetraazacyclotetradecane

2021 ◽  
Author(s):  
◽  
Asokamali Siriwardena
Keyword(s):  
Rate Constants ◽  
Magnetic Measurements ◽  
Order Rate Constant ◽  
Acidic Solutions ◽  
First Order ◽  
Order Rate ◽  
Pendant Arm ◽  
Nickel Copper ◽  
13C Nuclear Magnetic Resonance ◽  
Kinetics Of

<p>The reaction of bis-(diaminoethane)nickel(II) chloride, ([Ni(en)2]Cl2 in methanol with formaldehyde and nitroethane in the presence of triethylamine proceeds readily to produce (6, 13-dimethyl-6, 13-dinitro-1, 4, 8, 11-tetraazacyclotetradecane)nickel(II) chloride, [Ni(dini)] - Cl2. Reduction of the nitro groups of this compound by catalytic hydrogenation yields three isomers of the pendant arm macrocyclic complex (6, 13-diamino-6, 13-dimethyl-1, 4, 8, 11-tetraazachyclotetradecane)nickel(II) chloride, designated a-, b- and c-[Ni(diam)]Cl2. These were separated by fractional crystallization. The aisomer was observed to isomerizes slowly in solution to the b- form. A parallel dissociation reaction of the a- isomer was also observed. The demetallation of a- and b- isomers of the diam complex of nickel by reaction with cyanide or concentrated acid at 140 degrees C produces the macrocycle meso-(6, 13-diamino-6, 13-dimethyl-1, 4, 8, 11-tetraazacyclotetra-decane), diam. A variety of hexamine, pentamine and tetramine complexes of diam with nickel(II), copper(II), cobalt(II) and (III), chromium(III), palladium(II), rhodium(III), zinc(II) and cadmium(II) were prepared. Hexamine and tetramine forms of labile metal complexes could be rapidly and reversibly interconverted by altering the pH. The hexamine cobalt(III) cation, [Co(diam)]3+ was by far the most inert of the prepared cobalt(III) complexes, remaining unaffected in hot acidic solutions. In contrast, a single pendant arm of the hexamine [Cr(diam)]3+ cation could be dissociated in acid. (Two possibly triamine complexes of lead were also prepared). These compounds were characterized by elemental analysis, magnetic measurements, electronic, infrared, 1H and 13C nuclear magnetic resonance spectra. The pendant arm protonation constants (log K) of diam and selected complexes of nickel, copper and palladium were calculated from potentiometric titration measurements at 25 degrees C. The log K values for diam at 25 degrees C (I = 0.1 M NaclO4) were 11.15, 9.7, 6.2 and 5.3. Kinetics of the parallel isomerization and dissociation of a-[Ni(dimH2)]4+ in HCl/NaCl solutions were monitored spectrophotometrically at 50 degrees C. The rate of reaction in acidic solutions showed a non-linear dependency on acid concentration. The observed first order rate constant (kobs) for disappearance of a-[Ni(diamH2)]4+ (by isomerization and dissociation) in 2.0 M HCl, 0.1 M NaOH and 2.0 M NaCl were 3.05 x 10-4, 2.0(3) x 10-2 and 5.0 x 10-5 s-1 respectively. The rate of the dissociation component of the reaction of a-[Ni(diamH2)]4+ in 2.0 M HCl at 50 degrees C was 1.82 x 10-7 s-1. Acid bydrolysis kinetics of (Cu[diamH2])(ClO4)4 in hydrochloric acid and perchloric acid at 50 and 70 degrees C were studied spectrophotometrically. The reactions were slow and the observed first order rate constants were to a first approximation independent of the particular acid or its concentration. The observed first order rate constants were 1 x 10-9 and 8 x 10-9 s-1 at 50 and 70 degrees C respectively. Questions about the nature of the reaction being followed have been raised.</p>

scholarly journals Kinetics of hydride transfer between nitrogen heteroaromatic cations

1988 ◽  
Vol 66 (10) ◽  
pp. 2524-2531 ◽  
Author(s):  
John W. Bunting ◽  
Mark A. Luscher
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Hydride Transfer ◽  
First Order ◽  
Order Rate ◽  
Rate Determining Step ◽  
Donor And Acceptor ◽  
Pseudo First Order ◽  
Saturation Effects ◽  
Kinetics Of

The kinetics of the reduction of the 3-cyano-1-methylquinolinium, 4-cyano-2-methylisoquinolinium, and 2-methyl-5-nitro-isoquinolinium cations by 9,10-dihydro-10-methylacridine, and also the reduction of these same three cations as well as the 10-methylacridinium cation by 5,6-dihydro-5-methylphenanthridine, have been investigated in 20% acetonitrile – 80% water, ionic strength 1.0, 25 °C. The reactions of the 2-methyl-5-nitroisoquinolinium cation with both reductants, and also of the 4-cyano-2-methylisoquinolinium cation with 9,10-dihydro-10-methylacridine, display kinetic saturation effects in the pseudo-first-order rate constants as a function of heterocyclic cation concentration. These effects are consistent with the formation of 1:1 association complexes between hydride donor and acceptor prior to the rate-determining step of the reduction. The second-order rate constants for these reactions, and also those for analogous heterocyclic cation reductions by 1,4-dihydronicotinamides, show systematic variations as a function of the hydride donor and acceptor species.

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.

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