Vulcanization of Elastomers XV. The Vulcanization of Natural and Synthetic Rubber with Sulfur in Presence of Organic Bases (I)

1958 ◽  
Vol 31 (2) ◽  
pp. 286-300 ◽  
Author(s):  
Walter Schelle ◽  
Martin Cherubim
Keyword(s):  
Activation Energy ◽  
Fractional Order ◽  
Rate Constant ◽  
Kinetic Studies ◽  
Secondary Amines ◽  
Primary Amines ◽  
Sulfur Concentration ◽  
Organic Bases ◽  
Fractional Orders ◽  
Basic Strength

Abstract The results obtained from preliminary kinetic studies of the vulcanization of natural rubber (NR) with sulfur in the presence of organic bases may be summarized as follows. 1) The change of concentration of sulfur with time during reaction with NR for an initial sulfur concentration of 2.5 g per 100 g of mixture follows a fractional reaction order, n, of 0.6 at all temperatures. This result and the findings of other authors suggest that the reaction of sulfur with rubber is autocatalytic. From the temperature dependence of the rate constant the activation energy is found to be 35.3 kcal. 2) In the presence of zinc oxide and with a similar initial sulfur concentration, the reaction is first order and the activation energy, namely 35.6 kcal, is practically the same. 3) In the presence of diphenylguanidine (DPG) during cure sulfur decrease is a reaction of fractional order, n=0.75, and the activation energy is 29.8 kcal. 4) For a given initial concentration of sulfur and at constant temperature the rate of sulfur decrease during vulcanization increases with rising DPG content and reaches a limiting value; i.e., the rate constant depends on DPG concentration. Also, for various base (DPG is basic) concentrations sulfur decrease is of various fractional orders, n=0.5…0.7, etc. 5) The influence of base on the rate of sulfur decrease is interpreted broadly as a case of intermediate-catalysis (Zwischenstoff-Katalyse). 6) Vulcanization with sulfur is unaffected by tertiary amines and secondary amines have only a slight effect. 7) Primary amines, depending on basic strength, are strong accelerators of the rate of sulfur decrease. 8) In the presence of organic bases (aromatic amines) other than DPG, sulfur decrease is of fractional order where n varies between 0.5 and 0.7.

PHOTO-INITIATED REACTIONS OF THIOLS AND OLEFINS: II. THE ADDITION OF METHANETHIOL TO UNCONJUGATED OLEFINS

1964 ◽  
Vol 42 (10) ◽  
pp. 2250-2255 ◽  
Author(s):  
D. M. Graham ◽  
R. L. Mieville ◽  
R. H. Pallen ◽  
C. Sivertz
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Rate Constant ◽  
Rate Constants ◽  
Kinetic Studies ◽  
Addition Product ◽  
Isomerization Reaction ◽  
Ethylene Propylene ◽  
Intermittent Illumination ◽  
Competing Reactions

Kinetic studies have been made of the addition of methanethiol to ethylene, propylene, and butene-2. The results obtained are consistent with the mechanism postulated for the isomerization reaction (1). The overall activation energy was found to be negative and could be explained in terms of two competing reactions of the adduct radical: thermal decomposition leading to [Formula: see text] and olefin and dehydrogenation of thiol yielding addition product. Only the ratio of the rate constants for these two reactions could be determined. The method of intermittent illumination was used to evaluate the termination rate constant for the combination of two [Formula: see text] radicals which was found to be (2.5 ± 0.7) × 1010 l mole−1 s−1.

Kinetics and Mechanism of the Cleavage of N-Phthaloylglycine in Buffers of Some Primary Amines

2002 ◽  
Vol 2002 (12) ◽  
pp. 593-595 ◽  
Author(s):  
M. Niyaz Khan ◽  
Norsaadah H. Ismail
Keyword(s):  
Kinetic Parameters ◽  
Rate Constant ◽  
Kinetic Studies ◽  
Order Rate Constant ◽  
Second Order ◽  
Kinetics And Mechanism ◽  
Primary Amines ◽  
Buffer Concentration ◽  
Nucleophilic Cleavage ◽  
The Relationship

Kinetic studies on the nucleophilic cleavage of N-phthaloylglycine (NPG) in buffers of 2-methoxyethylamine, and 2-hydroxyethylamine reveal the relationship: knapp = A1 [Am]T/(1 + A2 [Am]T) where A1 and A2 are constants (kinetic parameters) and knapp and [Am]T represent apparent nucleophilic second-order rate constant and total amine buffer concentration, respectively.

Acceptorless amine dehydrogenation and transamination using Pd-doped layered double hydroxides

2018 ◽  
Author(s):  
Diana Ainembabazi ◽  
Nan An ◽  
Jinesh Manayil ◽  
Kare Wilson ◽  
Adam Lee ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Oxidation States ◽  
Secondary Amines ◽  
Primary Amines ◽  
Acid Dissolution ◽  
Oxidative Amination ◽  
Strong Function ◽  
Excellent Activity ◽  
High Yields ◽  
Double Hydroxides

<div> <p>The synthesis, characterization, and activity of Pd-doped layered double hydroxides (Pd-LDHs) for for acceptorless amine dehydrogenation is reported. These multifunctional catalysts comprise Brønsted basic and Lewis acidic surface sites that stabilize Pd species in 0, 2+, and 4+ oxidation states. Pd speciation and corresponding cataytic performance is a strong function of metal loading. Excellent activity is observed for the oxidative transamination of primary amines and acceptorless dehydrogenation of secondary amines to secondary imines using a low Pd loading (0.5 mol%), without the need for oxidants. N-heterocycles, such as indoline, 1,2,3,4-tetrahydroquinoline, and piperidine, are dehydrogenated to the corresponding aromatics with high yields. The relative yields of secondary imines are proportional to the calculated free energy of reaction, while yields for oxidative amination correlate with the electrophilicity of primary imine intermediates. Reversible amine dehydrogenation and imine hydrogenation determine the relative imine:amine selectivity. Poisoning tests evidence that Pd-LDHs operate heterogeneously, with negligible metal leaching; catalysts can be regenerated by acid dissolution and re-precipitation.</p> </div> <br>

scholarly journals A fractional order epidemic model for the simulation of outbreaks of Ebola

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Weiqiu Pan ◽  
Tianzeng Li ◽  
Safdar Ali
Keyword(s):  
Numerical Solution ◽  
Root Mean Square ◽  
Fractional Order ◽  
Relative Error ◽  
Numerical Solutions ◽  
Real Data ◽  
Mean Square ◽  
Order Model ◽  
The Real ◽  
Fractional Orders

AbstractThe Ebola outbreak in 2014 caused many infections and deaths. Some literature works have proposed some models to study Ebola virus, such as SIR, SIS, SEIR, etc. It is proved that the fractional order model can describe epidemic dynamics better than the integer order model. In this paper, we propose a fractional order Ebola system and analyze the nonnegative solution, the basic reproduction number $R_{0}$ R 0 , and the stabilities of equilibrium points for the system firstly. In many studies, the numerical solutions of some models cannot fit very well with the real data. Thus, to show the dynamics of the Ebola epidemic, the Gorenflo–Mainardi–Moretti–Paradisi scheme (GMMP) is taken to get the numerical solution of the SEIR fractional order Ebola system and the modified grid approximation method (MGAM) is used to acquire the parameters of the SEIR fractional order Ebola system. We consider that the GMMP method may lead to absurd numerical solutions, so its stability and convergence are given. Then, the new fractional orders, parameters, and the root-mean-square relative error $g(U^{*})=0.4146$ g ( U ∗ ) = 0.4146 are obtained. With the new fractional orders and parameters, the numerical solution of the SEIR fractional order Ebola system is closer to the real data than those models in other literature works. Meanwhile, we find that most of the fractional order Ebola systems have the same order. Hence, the fractional order Ebola system with different orders using the Caputo derivatives is also studied. We also adopt the MGAM algorithm to obtain the new orders, parameters, and the root-mean-square relative error which is $g(U^{*})=0.2744$ g ( U ∗ ) = 0.2744 . With the new parameters and orders, the fractional order Ebola systems with different orders fit very well with the real data.

Cyclic amidines derived from benz[c,d]indole and 4,5-dihydro-3H-1-benzazepine including some related compounds: Synthesis and pharmacological screening

1985 ◽  
Vol 50 (8) ◽  
pp. 1888-1898 ◽  
Author(s):  
Miroslav Protiva ◽  
Zdeněk Šedivý ◽  
Jiří Holubek ◽  
Emil Svátek ◽  
Jiří Němec
Keyword(s):  
Titanium Tetrachloride ◽  
Aqueous Sodium Hydroxide ◽  
Secondary Amines ◽  
Primary Amines ◽  
Open Chain ◽  
Lithium Aluminium ◽  
Pharmacological Screening ◽  
Antiinflammatory Effects ◽  
Related Compounds ◽  
Sodium Amide

Reactions of naphthostyril (I) with primary and secondary amines and titanium tetrachloride afforded cyclic amidines III-IX. Hydrogenation of I on Pd-C resulted in the 6,7,8,8a-tetrahydro derivative X which gave by treatment with sodium amide and 3-dimethylaminopropyl chloride the N-(aminoalkyl) compound XI. Reduction of I and its N-methyl derivative II with sodium amalgam in aqueous sodium hydroxide gave the 2a,3,4,5-tetrahydro derivatives XII and XIII. Reaction of XIII with sodium amide and 3-dimethylaminopropyl chloride afforded the 2a-(aminoalkyl) compound XIV. 1,3,4,5-Tetrahydro-1-benzazepin-2-one (XV) treated with primary amines and titanium tetrachloride gave the amidines XVI-XVIII. 3-Methyl-7,8,9,9a-tetrahydro-1H-benz[d,e]isoquinoline (XIX) was reduced with sodium borohydride to compound XX which was alkylated with propargyl bromide to 1-methyl-2-propargyl-2,3,3a,4,5,6-hexahydro-1H-benz[d,e]isoquinoline (XXI). An attempt to prepare the 2-(2-phenylethyl) analogue by treatment of compound XX with phenylacetyl chloride and by the following reduction with lithium aluminium hydride resulted in the open-chain amine XXII. The lactams I, II, X, and XIII showed some discoordinating, hypothermic, peripheral vasodilating, hyperglycaemic, diuretic and antiinflammatory effects. The amidines III-IX and XVI-XVIII had local anaesthetic, slight hypotensive, antiarrhythmic, peripheral myorelaxant, papaverine-like spasmolytic and thiopental potentiating effects.

THE OXIDATION OF NITRITE AND IODATE IONS BY HYPOCHLORITE IONS

1961 ◽  
Vol 39 (8) ◽  
pp. 1645-1651 ◽  
Author(s):  
M. W. Lister ◽  
P. Rosenblum
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Slow Stage ◽  
Iodate Ions

The oxidation of nitrite ions and of iodate ions by hypochlorite ions in aqueous solution has been examined. The oxidation of nitrite is really a reaction of hypochlorous acid, with the slow stage HOCl + NO2− + H2O → H3O+ + Cl− + NO3−. The rate constant is given by log k = 7.36−6450/RT (time in minutes, and the activation energy in calories). The oxidation of iodate is chiefly a reaction of hypochlorite ions, probably ClO− + IO3− → Cl− + IO4−, although the rate is somewhat increased by a higher concentration of hydroxide ions. The rate constant is given by log k = 16.15−26,100/RT. These results are compared with other oxidations by hypochlorite ions, to see if any general trends are apparent.

Alkene Difunctionalization Directed by Free Amines: Diamine Synthesis via Nickel-Catalyzed 1,2-Carboamination

2021 ◽  
Author(s):  
Taeho Kang ◽  
José Manuel González ◽  
Zi-Qi Li ◽  
Klement Foo ◽  
Peter Cheng ◽  
...  
Keyword(s):  
Nickel Catalyst ◽  
Room Temperature ◽  
Kinetic Studies ◽  
Fine Tuning ◽  
Secondary Amines ◽  
Protecting Group ◽  
Wide Range ◽  
Leaving Group ◽  
Primary And Secondary Amines ◽  
Reaction Proceeds

A versatile method to access differentially substituted 1,3- and 1,4-diamines via a nickel-catalyzed three-component 1,2-carboamination of alkenyl amines with aryl/alkenylboronic ester nucleophiles and N–O electrophiles is reported. The reaction proceeds efficiently with free primary and secondary amines without needing a directing auxiliary or protecting group, and is enabled by fine-tuning the leaving group on the N–O reagent. The transformation is highly regioselective and compatible with a wide range of coupling partners and alkenyl amine substrates, all performed at room temperature. A series of kinetic studies support a mechanism in which alkene coordination to the nickel catalyst is turnover-limiting.

Titration syntheses of polyaminosubstituted phthalocyanines via nucleophilic aromatic substitutions on zinc(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluorophthalocyanine

2007 ◽  
Vol 11 (07) ◽  
pp. 537-546 ◽  
Author(s):  
Clifford C. Leznoff ◽  
Annette Hiebert ◽  
Sibel Ok
Keyword(s):  
Amino Acids ◽  
Chain Length ◽  
Secondary Amines ◽  
Primary Amines ◽  
Tertiary Butyl ◽  
Butyl Esters ◽  
Mild Conditions ◽  
Nucleophilic Aromatic Substitutions

Primary amines, secondary amines and tertiary butyl esters of amino acids are used as nucleophiles with zinc(II) hexadecafluorophthalocyanine to provide mixtures of mono and disubstituted fluorinated phthalocyanines under mild conditions, or polyaminosubstituted phthalocyanines when using the amines as solvents. Diamines give cyclic substituted phthalocyanines, binuclear or trinuclear phthalocyanines or mixtures of both types, depending on the chain length or structure of the diamine.

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