scholarly journals N.M.R. studies of ligand exchange on acetylacetonatotrimethylplatinum(IV)

1975 ◽  
Vol 28 (4) ◽  
pp. 759 ◽  
Author(s):  
NS Ham ◽  
JR Hall ◽  
GA Swile
Keyword(s):  
Activation Energy ◽  
Quantitative Analysis ◽  
Ligand Exchange ◽  
Variable Temperature ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Cdcl3 Solution ◽  
Made In

A quantitative analysis of the variable-temperature 1H N.M.R. spectra of acetylacetonatotrimethyl-platinum(IV) has been made. In CDCl3 solution the exchange of acetylacetonate ligands is a first-order reaction and proceeds predominantly by dissociation of the dimer into two separated five-coordinate activated complexes. The activation energy is 61.5 � 0.8 kJ mol-1.

scholarly journals Pyrolysis of phenylmercaptoacetic acid

1968 ◽  
Vol 46 (2) ◽  
pp. 191-197 ◽  
Author(s):  
A. T. C. H. Tan ◽  
A. H. Sehon
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Carbon Monoxide ◽  
Acetic Acid ◽  
Rate Constant ◽  
Order Reaction ◽  
First Order Reaction ◽  
Kcal Mole ◽  
Dissociation Process ◽  
First Order

The pyrolysis of phenylmercaptoacetic acid was investigated by the toluene-carrier technique over the temperature range 760–835 °K. The main products of the decomposition were phenyl mercaptan, carbon dioxide, acetic acid, phenyl methyl sulfide, carbon monoxide, and dibenzyl.The overall decomposition was a first-order reaction with respect to phenylmercaptoacetic acid and could be represented by the two parallel steps:[Formula: see text]Reaction [1] was shown to be a homogeneous first-order dissociation process, and its rate constant was represented by the expression[Formula: see text]The activation energy of this reaction, i.e. 58 kcal/mole, was identified with D(C6H5S—CH2COOH).

Performance and Persistence of Atrazine

Weed Science ◽  
1973 ◽  
Vol 21 (5) ◽  
pp. 413-416 ◽  
Author(s):  
G. A. Buchanan ◽  
A. E. Hiltbold
Keyword(s):  
Half Life ◽  
Field Experiments ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Time Of Application ◽  
Made In

Field experiments were conducted from 1967 to 1971 to determine the influence of incorporation and time of application on the performance and persistence of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Both grass and broadleaf weeds were effectively controlled by atrazine on all dates of application. Both the 2.8 and 5.6 kg/ha rates were effective as preplant incorporated or preemergence treatments. Persistence of atrazine did not differ with respect to method of application. Applications of atrazine made in April and May were degraded more rapidly than were applications made in February and March. Loss curves generally corresponded to a first-order reaction with atrazine showing an average half-life of 20 days from February to July.

Studies of the Vulcanization of High Elastic Polymers. IV. Investigations with Model Compounds

1956 ◽  
Vol 29 (1) ◽  
pp. 37-48 ◽  
Author(s):  
Walter Scheele ◽  
Otto Lorenz
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Temperature Range ◽  
The Moment ◽  
The One ◽  
Tetraethylthiuram Disulfide ◽  
Limiting Value

Abstract If we disregard for the moment the phenomena which occur in the interaction of thiuram disulfide with geraniol under the influence of air and confine our consideration to the results which can be deduced from the study of this reaction in a stream of nitrogen, we are led to the conclusion that geraniol, which was used as a model compound, behaves with respect to its interaction with tetraethylthiuram disulfide, not only qualitatively but also quantitatively, exactly like rubber, and that it is not to be assumed that other tetraalkylthiuram disulfides as well as other compounds which are analogous to geraniol will behave differently. Thus the results can be evaluated as a proof that the vulcanization of natural rubber by thiuram disulfides depends on nothing other than a definite and always similar interaction with the allyl groups of the polyisoprene chain. The results of the investigation described in this paper can be regarded, moreover, as support for the correctness of our procedure in the clarification of the vulcanization mechanisms, and they stress the importance of analytical-chemical methods, which have certainly not been pursued in the past with the necessary intensity and insight. These investigations are being continued. It has already been found that the vulcanization of natural rubber with thiuram monosulfides and sulfur leads to the same results as vulcanization with thiuram disulfides. This has been conjectured, to be sure, by a number of workers. However, it was never really demonstrated experimentally. We shall report on this in the near future. The experimental results can now be summarized as follows : 1. The reaction between thiuram disulfide and geraniol (demonstrated by the example of tetraethylthiuram disulfide) takes place qualitatively and quantitatively like the interaction between thiuram disulfide and natural rubber. In the vulcanization of rubber by thiuram disulfides, therefore, there is involved a reaction of the thiuram disulfide with the allyl groups, leading to a definite conversion. 2. It was found that in the interaction of geraniol with thiuram disulfide under nitrogen and in the presence of zinc oxide, the limiting value of zinc dithiocarbamate amounts to 66 mole-per cent of the original thiuram disulfide, independent of the temperature. This was the result found in the study of the reaction of the thiuram disulfides with rubber. 3. We were able to show that the limiting value of the dithiocarbamate yield in the interaction of tetraethylthiuram disulfide with geraniol is independent of the thiuram disulfide concentration. This is likewise true for the reaction of the thiuram disulfides with natural rubber. From this it follows that the interaction of thiuram disulfides with allyl groupings, as they occur in the polyisoprene chain, is apparently a stoichiometric one. For this reason we can no longer retain the assumption that the limiting value of the yield of dithiocarbamate is the result of a sterically hindered reaction. 4. The change of concentration of zinc dithiocarbamate in the interaction of tetraethylthiuram disulfide with geraniol under nitrogen can be accounted for by postulating a reaction of the first order. The velocity constants were calculated and it was found that the resulting activation energy is somewhat greater than the one for the interaction with natural rubber. 5. Similarly the concentration of thiuram disulfide obeys a first-order reaction as it falls off to zero. The velocity constants were calculated. The activation energy obtained from the temperature dependence is in good agreement with that found for the interaction with rubber. 6. In the presence of oxygen, the reaction between thiuram disulfide and geraniol takes a quite different course. The rate of decrease of concentration of thiuram disulfide, which likewise follows a first-order reaction, is higher. The yield of zinc dithiocarbamate does not attain the constant value of 66 mole-per cent of the original thiuram disulfide. In the temperature range studied, the amount of dithiocarbamate found is smaller. The limiting value reached at the various temperatures is progressively smaller, the lower the temperature chosen. Whether by expanding the temperature range, one would eventually reach a minimum and a maximum limiting value has not been investigated.

Vulcanization of Elastomers. 21. Vulcanization of Natural Rubber with Thiuram Disulfides. VI

1959 ◽  
Vol 32 (2) ◽  
pp. 566-576
Author(s):  
Walter Scheele ◽  
Klaus Hummel
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Temperature Dependence ◽  
Sulfur Content ◽  
Rate Constants ◽  
Order Reaction ◽  
First Order Reaction ◽  
Kcal Mole ◽  
First Order ◽  
Limiting Value

Abstract Bound sulfur in a pure thiuram vulcanizate increases relatively rapidly at first at all temperatures, reaches a poorly defined maximum at about 27 to 30%, independent of temperature, and then recedes slightly to reach a limiting value of 25% also independent of temperature, based on the original thiuram disulfide. The rise in sulfur content at the start points to a temperature-independent limiting value of 33%. It is shown that the combination of sulfur in this region initially follows a first order reaction, and goes at the same rate as the reduction in concentration of thiuram disulfide. It can be seen from the above that sulfur may be combined in thiuram vulcanization without simultaneous crosslinking. The dithiocarbamate formation increases rapidly in the region of longer vulcanization times, after the maximum in bound sulfur has been reached, without further combination of sulfur with the vulcanizate. The rate constants for thiuram decrease, for dithiocarbamate increase and for sulfur combination were calculated. The temperature dependence of each of these reactions has practically the same activation energy, 23 kcal/mole. The bound sulfur content of the vulcanizates in pure thiuram vulcanizations is no criterion of the state of vulcanization.

Vulcanization Kinetics of Natural Rubber Coagulated by Microorganisms with Use of a Vulcameter

2010 ◽  
Vol 160-162 ◽  
pp. 1181-1186 ◽  
Author(s):  
Zhi Feng Wang ◽  
Si Dong Li ◽  
Xiao Dong She
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Rate Constants ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Second Stage ◽  
End Stage ◽  
Two Stages ◽  
Kinetics Of

Kinetics of vulcanization of natural rubber coagulated by microorganisms (NR-m) was studied with the use of a vulcameter. In the induction period of vulcanization, the time t0 of NR-m is shorter than that of natural rubber coagulated by acid (NR-a), and the rate constant k1/a of NR-m are greater than that of NR-a. Both the curing periods of NR-m and NR-a consist of two stages. The first stage follows first-order reaction. The rate constants k2 of NR-m in the first stage are greater than that of NR-a at the same temperature, and so are the activation energy E2. The second stage (end stage of the curing period) does not follow first-order reaction, and the calculated reaction order n of NR-m is in the range of 0.82-0.85, and that of NR-a is in the range of 0.64-0.72. The rate constants k3 of the second stage for NR -m are greater than that of NR-a at the same temperature, and so is the activation energy E3.

Leaching Kinetics of Atrazine and Inorganic Chemicals in Tilled and Orchard Soils

2014 ◽  
Vol 28 (2) ◽  
pp. 231-237 ◽  
Author(s):  
Lech W. Szajdak ◽  
Jerzy Lipiec ◽  
Anna Siczek ◽  
Artur Nosalewicz ◽  
Urszula Majewska
Keyword(s):  
Reaction Rate ◽  
Inorganic Compounds ◽  
Model Performance ◽  
Order Reaction ◽  
First Order Reaction ◽  
Order Kinetic ◽  
Time Data ◽  
First Order ◽  
Concentration Changes ◽  
Reaction Constants

Abstract The aim of this study was to verify first-order kinetic reaction rate model performance in predicting of leaching of atrazine and inorganic compounds (K+1, Fe+3, Mg+2, Mn+2, NH4 +, NO3 - and PO4 -3) from tilled and orchard silty loam soils. This model provided an excellent fit to the experimental concentration changes of the compounds vs. time data during leaching. Calculated values of the first-order reaction rate constants for the changes of all chemicals were from 3.8 to 19.0 times higher in orchard than in tilled soil. Higher first-order reaction constants for orchard than tilled soil correspond with both higher total porosity and contribution of biological pores in the former. The first order reaction constants for the leaching of chemical compounds enables prediction of the actual compound concentration and the interactions between compound and soil as affected by management system. The study demonstrates the effectiveness of simultaneous chemical and physical analyses as a tool for the understanding of leaching in variously managed soils.

The Kinetics of Glucose Decomposition with Sulfate Reduction in the Anaerobic Fluidized Bed Reactor

1993 ◽  
Vol 28 (2) ◽  
pp. 135-144 ◽  
Author(s):  
S. Matsui ◽  
R. Ikemoto Yamamoto ◽  
Y. Tsuchiya ◽  
B. Inanc
Keyword(s):  
Sulfate Reduction ◽  
Fluidized Bed ◽  
Kinetic Equations ◽  
Fluidized Bed Reactor ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Glucose Decomposition ◽  
Reaction Equations ◽  
Kinetics Of

Using a fluidized bed reactor, experiments on glucose decomposition with and without sulfate reduction were conducted. Glucose in the reactor was mainly decomposed into lactate and ethanol. Lactate was mainly decomposed into propionate and acetate, while ethanol was decomposed into propionate, acetate, and hydrogen. Sulfate reduction was not involved in the decomposition of glucose, lactate, and ethanol, but was related to propionate and acetate decomposition. The stepwise reactions were modeled using either a Monod expression or first order reaction kinetics in respect to the reactions. The coefficients of the kinetic equations were determined experimentally. The modified Monod and first order reaction equations were effective at predicting concentrations of glucose, lactate, ethanol, propionate, acetate, and sulfate along the beight of the reactor. With sulfate reduction, propionate was decomposed into acetate, while without sulfate reduction, accumulation of propionate was observed in the reactor. Sulfate reduction accelerated propionate conversion into acetate by decreasing the hydrogen concentration.

Complete monotonicity of entropy production in chemical reaction

1981 ◽  
Vol 46 (2) ◽  
pp. 452-456
Author(s):  
Milan Šolc
Keyword(s):  
Entropy Production ◽  
Equilibrium Constant ◽  
Chemical Reaction ◽  
Relative Entropy ◽  
Order Reaction ◽  
Complete Monotonicity ◽  
First Order Reaction ◽  
First Order ◽  
Completely Monotonic ◽  
Derivatives Of

The successive time derivatives of relative entropy and entropy production for a system with a reversible first-order reaction alternate in sign. It is proved that the relative entropy for reactions with an equilibrium constant smaller than or equal to one is completely monotonic in the whole definition interval, and for reactions with an equilibrium constant larger than one this function is completely monotonic at the beginning of the reaction and near to equilibrium.

Kinetics and Mechanism of Hexachloroiridate(IV) Oxidation of Arsenic(III) in Acidic Perchlorate Solutions

1992 ◽  
Vol 57 (7) ◽  
pp. 1451-1458 ◽  
Author(s):  
Refat M. Hassan
Keyword(s):  
Ionic Strength ◽  
Fractional Order ◽  
Activation Parameters ◽  
Order Reaction ◽  
First Order Reaction ◽  
Intermediate Complex ◽  
Constant Ionic Strength ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Kinetics Of

The kinetics of oxidation of arsenic(III) by hexachloroiridate(IV) at lower acid concentrations and at constant ionic strength of 1.0 mol dm-3 have been investigated spectrophotometrically. A first-order reaction in [IrCl62-] and fractional order with respect to arsenic(III) have been observed. A kinetic evidence for the formation of an intermediate complex between the hydrolyzed arsenic(III) species and the oxidant was presented. The results showed that decreasing the [H+] is accompanied by an appreciable acceleration of the rate of oxidation. The activation parameters have been evaluated and a mechanism consistent with the kinetic results was suggested.

scholarly journals Determination of exothermic batch reactor specific model parameters

2019 ◽  
Vol 292 ◽  
pp. 01063
Author(s):  
Lubomír Macků
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Specific Model ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
First Order Reaction ◽  
Model Parameters ◽  
Reactor Model ◽  
First Order

An alternative method of determining exothermic reactor model parameters which include first order reaction rate constant is described in this paper. The method is based on known in reactor temperature development and is suitable for processes with changing quality of input substances. This method allows us to evaluate the reaction substances composition change and is also capable of the reaction rate constant (parameters of the Arrhenius equation) determination. Method can be used in exothermic batch or semi- batch reactors running processes based on the first order reaction. An example of such process is given here and the problem is shown on its mathematical model with the help of simulations.

Sign in / Sign up

Export Citation Format

Share Document