The Chemistry of Vulcanization. VIII. Role of Zinc Butyrate in the Reaction of Diphenylmethane, Sulfur and 2-Benzothiazolyl Disulfide

Abstract Diphenylmethane (DPM) which contains α-methylenic hydrogen has been used as a model of rubber hydrocarbon, and reactions involving DPM, sulfur and thiazole type accelerators in the absence of zinc oxide or soap were reported in previous papers. These papers reported that 2-mercaptobenzothiazole (MBT), 2-benzothiazolyl disulfide (MBTS) and zinc salt of 2-mercaptobenzothiazole (ZMBT) generate the same radical, i.e., 2-benzothiazolesulfenyl which has the accelerating effect. This radical opens the ring of elementary sulfur and thus accelerates vulcanization since the spontaneous splitting of the sulfur ring molecule to a biradical was found to be the rate determining step in the reaction of DPM with sulfur alone. Processes by which accelerators generate this radical differ from each other owing to the types of accelerators, that is, mercaptan, disulfide and zinc mercaptide type. The previous paper reported the reaction involving DPM, sulfur and MBT in the presence of zinc butyrate. According to this, MBT first reacts with zinc butyrate to form butyric acid and ZMBT, the latter then generating the effective benzothiazole-sulfenyl radical. Thus, even in the presence of zinc soap, the essential mechanism of acceleration is the same as in the absence of zinc soap, though the process and rate for forming benzothiazolesulfenyl radical are different in the absence of zinc soap. In the present paper the reaction of DPM, sulfur and MBTS in the presence of zinc butyrate are reported. The reaction mechanism will be deduced from the experimental results obtained here and from conclusions obtained in the previous papers. The rate equation for MBTS consumption and equation for the accelerating efficiency for this accelerator are derived from the mechanism. The theoretical equations were examined by experiments.

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The Chemistry of Vulcanization. VII. Role of Zinc Butyrate in the Reaction of Diphenylmethane, Sulfur and 2-Mercaptobenzothiazole

Rubber Chemistry and Technology ◽

10.5254/1.3542128 ◽

1960 ◽

Vol 33 (1) ◽

pp. 217-228 ◽

Cited By ~ 3

Author(s):

Jitsuo Tsurugi ◽

Haruko Fukuda

Keyword(s):

Zinc Oxide ◽

Kinetic Study ◽

Butyric Acid ◽

Model Compound ◽

Reaction System ◽

The Other ◽

Zinc Salt ◽

Reaction Products ◽

Molecular Dispersion

Abstract In previous Parts of this series, the accelerating mechanism of thiazole type accelerators, namely, 2-mercaptobenzothiazole (MBT), 2,2′-benzothiazolyl disulfide (MBTS) and zinc salt of 2-mercaptobenzothiazole (ZMBT) in the absence of zinc oxide or zinc soap, was investigated with diphenylmethane (DPM) as a model compound of rubber hydrocarbon. The significance of DPM as a model was discussed in some of the earlier papers. Parts IV, V and VI of this series indicated that 2-mercaptobenzothiazolyl radical generated from accelerators splits the sulfur ring, and that the processes by which accelerators generate the radical differ with each other according to their types. These results were obtained in the absence of zinc oxide or zinc soap. The present study will report the role of zinc butyrate in the reaction involving DPM, sulfur and MBT. Experience in the industry indicates that zinc oxide (or zinc soap) is indispensable to the thiazole type accelerators and that the efficiency of zinc oxide or soap is more prominent in MBT than in MBTS or ZMBT. The results obtained in the previous papers also suggest that zinc oxide or soap may have an influence on the rate at which the accelerator generates 2-mercaptobenzothiazolyl radical, since it is shown in Parts IV, V and VI that the radical has an accelerating effect. Therefore, it may be considered that zinc oxide or zinc soap activates MBT more effectively than does the other thiazole type accelerators in order to produce this radical. As will be seen later in this study, interaction of MBT with zinc butyrate in the absence of sulfur produces ZMBT and butyric acid. The ZMBT will interact with sulfur and generate the 2-mercaptobenzothiazolyl radical as reported in Part VI. The zinc salt thus formed will be dispersed in a state of molecular dispersion in the reaction system, while the same compound prepared in Part VI was not dissolved in DPM even at the reaction temperatures. In this respect the former is considered more effective than the latter. In order to verify the above assumptions the reaction involving DPM, sulfur and MBT in the presence of zinc butyrate were investigated. The reaction products and mechanism were compared with those in the absence of zinc soap. Since zinc butyrate is soluble in the reaction system at the reaction temperatures, a kinetic study also was carried out and compared with that in the absence of zinc soap.

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From the Understanding of the Reaction Mechanism Towards Optimizing the Deposition Rate and Optoelectronic Properties of a-Si:H

MRS Proceedings ◽

10.1557/proc-149-3 ◽

1989 ◽

Vol 149 ◽

Cited By ~ 6

Author(s):

S. Veprek ◽

M. Heintze ◽

R. Bayer ◽

N. Jurčik-Rajman

Keyword(s):

Reaction Mechanism ◽

Surface Coverage ◽

Kinetic Studies ◽

Reactive Intermediates ◽

Sticking Coefficient ◽

High Quality ◽

Rate Determining Step ◽

Homogeneous Good ◽

Good Agreement

ABSTRACTWe present new results of kinetic studies of the deposition of high quality a-Si:H which strongly support the reaction mechanism suggested in our earlier papers: 1. SiH4 → SiH2; 2. SiH2 + SiS4 → Si2H6 (SiH2 + Si2H6 → Si3H6); 3. Si2H6 → 2a-Si:H (Si3H8 → 3a-Si:H). The “SiH3 mechanism”, as promoted by several workers, is in contradiction with these experimental facts.The di- and trisilane, which have a much higher reactive sticking coefficient than monosilane, play the role of reactive intermediates which facilitate the heterogeneous decomposition of silicon carrying species at the surface of the growing film. The values of the reactive sticking coefficient of Si2H6 and Si3H8 depend on the surface coverage by chemisorbed hydrogen; they increase with decreasing surface coverage. Under the conditions of the growth of high quality a-Si:H films the reactive sticking coefficient of disilane amounts to 10−4 to 10−2 which is in a good agreement with recent data of other authors.The rate determining step of the growth of high quality a-Si:H films is the desorption of hydrogen from the surface of the growing film. This can be strongly enhanced by ion bombardment at impact energy of <100 eV. In this way, homogeneous, good quality films were deposited at rates up to 1800 Angströms/min, and there is a well justified hope that this rate can be further increased.

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KINETIC STUDY OF THE ISOMERIZATION OF n-BUTENES ON CHROMIA–ALUMINA

Canadian Journal of Chemistry ◽

10.1139/v62-327 ◽

1962 ◽

Vol 40 (11) ◽

pp. 2130-2139 ◽

Cited By ~ 6

Author(s):

Y. Amenomiya ◽

R. J. Cvetanović

Keyword(s):

Kinetic Study ◽

Rate Equation ◽

Pressure Range ◽

Experimental Results ◽

Alumina Catalyst ◽

Adsorbed Species ◽

Temperature Range ◽

Rate Determining Step

Mutual interconversions of the three n-butenes on a chromia–alumina catalyst have been studied in a temperature range between 210 and 260 °C and in a pressure range from about 10 to about 100 mm. Dependence of initial rates on the initial pressures of the reactants was determined experimentally. The initial rates of isomerization could be, in each case, expressed empirically by a rate equation conforming to the Langmuir–Hinshelwood formula. It was possible to explain the experimental results by assuming the existence of three different adsorbed species for the three n-butene isomers and their surface interconversions as the rate-determining step.

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Reaction mechanism of nitrile hydratase : role of the stabilizing agent, n-butyric acid

Seibutsu Butsuri ◽

10.2142/biophys.40.s29_3 ◽

2000 ◽

Vol 40 (supplement) ◽

pp. S29

Author(s):

M. Odaka ◽

H. Nakayama ◽

N. Watanabe ◽

Y. Kawano ◽

K. Takio ◽

...

Keyword(s):

Reaction Mechanism ◽

Butyric Acid ◽

Nitrile Hydratase ◽

Stabilizing Agent

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A DFT/MM analysis of the effect of ligand substituents on asymmetric hydrogenation catalyzed by rhodium complexes with phosphine–phosphinite ligands

Canadian Journal of Chemistry ◽

10.1139/v09-051 ◽

2009 ◽

Vol 87 (10) ◽

pp. 1273-1279 ◽

Cited By ~ 22

Author(s):

Steven M. A. Donald ◽

Anton Vidal-Ferran ◽

Feliu Maseras

Keyword(s):

Dft Calculations ◽

Asymmetric Hydrogenation ◽

Rhodium Catalyst ◽

Experimental Results ◽

Catalytic Process ◽

Rhodium Complexes ◽

Electronic Effects ◽

Rate Determining Step ◽

Bidentate Phosphine

DFT and DFT/MM calculations are carried out on the rate-determining step of the addition of dihydrogen to methyl-(N)-acetylaminoacrylate catalyzed by a rhodium catalyst containing a bidentate phosphine–phosphinite ligand. DFT calculations reproduce the experimental results, while DFT/MM calculations do not. The failure of DFT/MM methods for this particular problem is analyzed through a series of calculations with different partitions between the DFT and MM regions, which show that electronic effects of all ligand substituents considered are critical. The analysis of these electronic effects provides key information on the role of each of the substituents in the outcome of the overall catalytic process.

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The Chemistry of Vulcanization. V. Action of 2,2′-Benzothiazolyl Disulfide on the Reaction of Diphenylmethane and Sulfur

Rubber Chemistry and Technology ◽

10.5254/1.3542339 ◽

1958 ◽

Vol 31 (4) ◽

pp. 788-799 ◽

Cited By ~ 6

Author(s):

Jitsuo Tsurugi ◽

Haruko Fukuda

Keyword(s):

Activation Energy ◽

Zinc Oxide ◽

Reaction Mechanism ◽

Rate Equation ◽

Thermal Dissociation ◽

Material Balance ◽

Reaction Products ◽

Kcal Mole ◽

Near Future

Abstract The reaction involving diphenylmethane, sulfur and 2,2′-benzothiazoIyl disulfide is summarized as follows. A. The reaction products and material balance among them are indicated. B. A reaction mechanism was decided upon. C. The rate equation for MBTS consumption was derived from the above mechanism and the results interpreted satisfactorily. The activation energy for thermal dissociation of 2,2′-benzothiazolyl disulfide was found to be 32.7 kcal/mole. D. The accelerating efficiency of this accelerator was defined, discussed and evaluated. These studies are being continued and further communications on the studies of accelerators in the presence of zinc oxide or zinc soap will appear in the near future.

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Transport and fluctuations in nonlinear-dissipative systems: role of interparticle collisions

Nonlinear Analysis Modelling and Control ◽

10.15388/na.1999.4.0.15249 ◽

1999 ◽

Vol 4 ◽

pp. 31-86 ◽

Cited By ~ 1

Author(s):

R. Katilius ◽

A. Matulionis ◽

R. Raguotis ◽

I. Matulionienė

Keyword(s):

Electric Fields ◽

Carrier Density ◽

Experimental Results ◽

Dissipative Systems ◽

Doped Semiconductors ◽

Electron Diffusion ◽

Electron Collisions ◽

Electric Noise ◽

Diffusion Phenomena

The goal of the paper is to overview contemporary theoretical and experimental research of the microwave electric noise and fluctuations of hot carriers in semiconductors, revealing sensitivity of the noise spectra to non-linearity in the applied electric field strength and, especially, in the carrier density. During the last years, investigation of electronic noise and electron diffusion phenomena in doped semiconductors was in a rapid progress. By combining analytic and Monte Carlo methods as well as the available experimental results on noise, it became possible to obtain the electron diffusion coefficients in the range of electric fields where inter-electron collisions are important and Price’s relation is not necessarily valid. Correspondingly, a special attention to the role of inter-electron collisions and of the non-linearity in the carrier density while shaping electric noise and diffusion phenomena in the non-equilibrium states will be paid. The basic and up-to-date information will be presented on methods and advances in this contemporary field - the field in which methods of non-linear analytic and computational analysis are indispensable while seeking coherent understanding and interpretation of experimental results.

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Full Kinetics and a Mechanism Investigation for the Generation of 4- Substituted 1, 4-Dihydropyridine Derivatives in the Presence of Green Catalyst and Aqueous Medium: Experimental Procedure

Current Organic Synthesis ◽

10.2174/1570179417666201231105013 ◽

2020 ◽

Vol 17 ◽

Author(s):

Sayyed Mostafa Habibi-Khorassani ◽

Mehdi Shahraki ◽

Sadegh Talaiefar

Keyword(s):

Reaction Mechanism ◽

Reaction Centre ◽

Green Catalyst ◽

Experimental Procedure ◽

Dominant Mechanism ◽

Rate Determining Step ◽

12 Steps ◽

Reaction Constant ◽

Substituted 1 ◽

Dihydropyridine Derivatives

Aims and Objective: The main objective of the kinetic investigation of the reaction among ethyl acetoacetate 1, ammoniumacetat 2, dimedone 3 and diverse substitutions of benzaldehyde 4-X, (X= H, NO2, CN, CF3, Cl, CH (CH3)2, CH3, OCH3, OCH3, and OH) for the generation of 4-substituted 1, 4-dihydropyridine derivatives (product 5) was the recognition of the most realistic reaction mechanism. The layout of the reaction mechanism studied kinetically by means of the UV-visible spectrophotometry approach. Materials and Methods: Among the various mechanisms, only mechanism1 (path1) involving 12 steps was recognized as a dominant mechanism (path1). Herein, the reaction between reactants 1 and 2 (kobs= 814.04 M-1 .min-1 ) and also compound 3 and 4-H (kobs= 151.18 M-1 .min-1 ) were the logical possibilities for the first and second fast steps (step1 and step2, respectively). Amongst the remaining steps, only step9 of the dominant mechanism (path1) had substituent groups (X) near the reaction centre that could be directly resonated with it. Results and Discussion: Para electron-withdrawing or donating groups on the compound 4-X increases the rate of the reaction 4 times more or decreases 8.7 times less than the benzaldehyde alone. So, this step is sensitive for monitoring any small or huge changes in the reaction rate. For this reason, step9 is the rate-determining step of the reaction mechanism (path1). Conclusion: The recent result is the agreement with the Hammett description with an excellent dual substituent factor (r = 0.990) and positive value of reaction constant (ρ = +0.9502) which confirmed both the resonance and inductive effects “altogether” contributed on the reaction centre of step9 in the dominant mechanism (path1).

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