THE KINETICS OF THE TERTIARY-AMINE-CATALYZED REACTION OF ORGANIC ISOCYANATES WITH THIOLS

1960 ◽  
Vol 38 (12) ◽  
pp. 2418-2424 ◽  
Author(s):  
Yoshio Iwakura ◽  
Hisao Okada
Keyword(s):  
Reaction Mechanism ◽  
Tertiary Amine ◽  
Relative Rate ◽  
Catalytic Action ◽  
Tertiary Amines ◽  
First Order ◽  
Kinetics Of

The kinetics of the reactions of isocyanates with thiols in the presence of tertiary amines were examined. The rate of the reaction was of the first order with respect to the concentration of isocyanate, thiol, and tertiary amine. The catalytic action of tertiary amines decreased in the order of triethylenediamine, triethylamine, diethylcyclohexylamine, tributylamine, N-methylmorpholine, pyridine, and quinoline. The relative rate of the reaction of phenylisocyanate with thiols decreased in the order of phenylmethanethiol, 1,4-butanedithiol, 1-butanethiol, 1-dodecanethiol, and thiophenol. The reaction took place more smoothly in strong ionizing solvents. These facts can be explained by the reaction mechanism indicated by the equations [6] to [8].

THE KINETICS OF THE REACTION OF ORGANIC ISOTHIOCYANATES WITH 1-OCTANOL IN o-DICHLOROBENZENE

1962 ◽  
Vol 40 (12) ◽  
pp. 2369-2375 ◽  
Author(s):  
Yoshio Iwakura ◽  
Hisao Okada
Keyword(s):  
Reaction Mechanism ◽  
Rate Constants ◽  
Catalytic Effect ◽  
Relative Rate ◽  
Slow Step ◽  
Dibutyltin Dilaurate ◽  
Kcal Mole ◽  
Large Excess ◽  
First Order ◽  
Kinetics Of

The kinetics of the reaction of organic isothiocyanates with a large excess of 1-octanol in o-dichlorobenzene was examined at 90–140°. The rate of the reaction was first order with respect to the concentration of isothiocyanate, but the apparent second-order rate constants calculated varied according to the initial 1-octanol concentration. These facts can be explained by a reaction mechanism involving two molecules of 1-octanol in the transition state for the slow step of the reaction. The relative rate of the reaction of isothiocyanates with 1-octanol at 120° decreased in the order of benzyl, phenyl, allyl, ethyl, n-butyl, n-hexyl, isobutyl, and cyclohexyl isothiocyanate. The apparent energies of activation and log A were obtained as 13.5–16.5 kcal/mole and 4.65–6.46 (A in liter/mole min), respectively. Tributylamine had a slight catalytic effect, but dibutyltin dilaurate and ferric acetylacetonate had a strong catalytic action in these reactions.

The kinetics of hydration of tricalcium silicate

1970 ◽  
Vol 48 (21) ◽  
pp. 3291-3299 ◽  
Author(s):  
K. G. McCurdy ◽  
B. P. Erno
Keyword(s):  
Reaction Mechanism ◽  
Intermediate Product ◽  
Activation Energies ◽  
Tricalcium Silicate ◽  
Rate Data ◽  
Large Excess ◽  
First Order ◽  
Kinetics Of ◽  
Subsequent Decomposition

An investigation has been made of the kinetics of hydration of tricalcium silicate at several temperatures in a large excess of water in the presence of various added ions. The rate data have been interpreted by a reaction mechanism which involves: (a) the first order hydration of tricalcium silicate to form an intermediate product, 1.5CaO•SiO2, which can react by two pathways, (b) the direct first order decomposition of intermediate, 1.5CaO•SiO2, to form lime and silica or (b′) complexing of intermediate with silica and subsequent decomposition to form lime and silica. This reaction mechanism predicts the rate of production of base during the hydration. The effect of various added ions is interpreted in terms of the proposed mechanism.Rate constants and activation energies for the various steps in the proposed mechanism are reported.

Kinetics and Mechanism of Oxidation of Selenium(IV) by Permanganate Ion in Aqueous Perchlorate Solutions

1993 ◽  
Vol 58 (3) ◽  
pp. 538-546 ◽  
Author(s):  
Refat M. Hassan ◽  
Sahr A. El-Gaiar ◽  
Abd El-Hady M. El-Summan
Keyword(s):  
Reaction Mechanism ◽  
Reaction Rate ◽  
Oxidation Process ◽  
Selenium Dioxide ◽  
Order Reaction ◽  
Acid Solutions ◽  
First Order ◽  
Acid Catalyzed ◽  
Mechanism Of Oxidation ◽  
Kinetics Of

The kinetics of permanganate oxidation of selenium dioxide in perchloric acid solutions at a constant ionic strength of 2.0 mol dm-3 has been investigated spectrophotometrically. A first-order reaction in [MnO4-] and fractional order with respect to selenium(IV) were observed. The reaction rate was found to be pH-independent at lower acid concentrations ([H+] < 0.5 mol dm-3) and was acid-catalyzed beyond this range. Addition of Mn2+ and F- ions leads to the prediction that MnO4- is the sole reactive species in the oxidation process. A tentative reaction mechanism consistent with the reaction kinetics has been proposed.

scholarly journals Kinetics of Oxidation of Tryptophan by Sodium Hypochlorite

1981 ◽  
Vol 36 (3) ◽  
pp. 359-361 ◽  
Author(s):  
Thomas Rausch ◽  
Frieder Hofmann ◽  
Willy Hilgenberg
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Sodium Hypochlorite ◽  
Arrhenius Plot ◽  
Ph Dependence ◽  
Order Conditions ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Pseudo First Order ◽  
Kinetics Of

AbstractThe oxidation of tryptophan to 3-indoleacetaldehyde with sodium hypochlorite was investigated with 14C labelled DL-tryptophan. The reaction was performed under pseudo first order conditions. From the pH dependence of the reaction it was concluded that only the unprotonated tryptophan is converted to the aldehyde. The activation energy is 35 ± 2.2 (SE) kJ x mol-1 as derived from the Arrhenius plot. Variing the pH between 8.5 and 11.0 and the temperature in the range from 298 K to 318 K did not alter the selectivity of the reaction as confirmed by TLC of the product (purity ≧ 90%). A possible reaction mechanism is proposed.

scholarly journals New Insight on the Study of the Kinetic of Biobased Polyurethanes Synthesis Based on Oleo-Chemistry

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4332 ◽  
Author(s):  
Julien Peyrton ◽  
Clémence Chambaretaud ◽  
Luc Avérous
Keyword(s):  
Methyl Oleate ◽  
Tertiary Amine ◽  
Large Range ◽  
Kinetic Studies ◽  
Polyurethane Foams ◽  
First Order ◽  
Model Molecule ◽  
Specific Order ◽  
Unsaturated Triglycerides ◽  
Kinetics Of

Nowadays, polyols are basic chemicals for the synthesis of a large range of polymers, such as polyurethane foams (PUF), which are produced with several other compounds, such as polyisocyanates. During the last decades, the oleo-chemistry has developed several routes from glycerides to polyols for the polyurethanes (PU) industry to replace mainly conventional fossil-based polyols. A large range of biobased polyols can be now obtained by epoxidation of the double bonds and ring-opening (RO) of the subsequent epoxides with different chemical moieties. In preliminary studies, the RO kinetics of an epoxidized model molecule (methyl oleate) with ethanol and acetic acid were investigated. Subsequently, polyols that were derived from unsaturated triglycerides were explored in the frame of e.g., PUF formulations. Different associations were studied with different mono-alcohols derived from epoxidized and ring-opened methyl oleate while using several ring-openers to model such systems and for comparison purposes. Kinetic studies were realized with the pseudo-first-order principle, meaning that hydroxyls are in large excess when compared to the isocyanate groups. The rate of isocyanate consumption was found to be dependent on the moiety located in β-position of the reactive hydroxyl, following this specific order: tertiary amine >> ether > ester. The tertiary amine in β-position of the hydroxyl tremendously increases the reactivity toward isocyanate. Consequently, a biobased reactive polyurethane catalyst was synthesized from unsaturated glycerides. These approaches offer new insights regarding the replacement of current catalysts often harmful, pungent, and volatile used in PU and PUF industry, in order to revisit this chemistry.

Oxidation of aromatic secondary and tertiary amines by peroxydisulphate. A kinetic study

1971 ◽  
Vol 24 (8) ◽  
pp. 1633 ◽  
Author(s):  
A Sabesan ◽  
N Venkatasubramanian
Keyword(s):  
Transition State ◽  
Kinetic Study ◽  
Tertiary Amines ◽  
Steric Strain ◽  
First Order ◽  
Kinetics Of

The kinetics of the oxidation of aromatic secondary and tertiary amines by peroxydisulphate ion under aqueous basic conditions have been investigated. The reaction is first order in amine and first order in S2O82- ion. The order of the reactivity is found to be: N-methylaniline > N,N-dimethylaniline > aniline and N-ethylaniline > N,N-diethylaniline > aniline, and among each class: N-methylaniline > N-ethylaniline and N,N-dimethylaniline > N,N-diethylaniline. This reactivity is explained on the basis of a steric strain in the transition state super- imposed over the usual polar effects.

Studies on the kinetics of racemization of 2,4-disubstituted-5(4H)-oxazolones

1988 ◽  
Vol 66 (10) ◽  
pp. 2540-2544 ◽  
Author(s):  
Marek Slebioda ◽  
Marc A. St-Amand ◽  
Francis M. F. Chen ◽  
N. Leo Benoiton
Keyword(s):  
Nitrogen Atom ◽  
Tertiary Amine ◽  
Thermodynamic Data ◽  
Activation Parameters ◽  
Steric Effects ◽  
Tertiary Amines ◽  
Electronic Effects ◽  
Catalyzed Reactions ◽  
Kinetics Of ◽  
Benzyl Substituent

The kinetics of racemization of 2,4-disubstituted-5(4H)-oxazolones obtained from N-acetyl, N-benzoyl, and N-benzyloxycarbonylglycyl-L-leucine, -valine, and -phenylalanine have been studied in several solvents alone and in the presence of tertiary amines. The influence of the nature of the substituents on the rate of the reaction has been evaluated, and the values of the activation parameters ΔH≠ and ΔS≠ for the base-catalyzed reactions have been determined. The racemization process is governed by electronic effects of the C(2)-substituents and steric effects of the C(4)-substituents of the oxazolones. The thermodynamic data suggest that the 2-substituted-4-benzyl-5(4H)-oxazolones racemize more readily than the 4-alkyl analogues (alkyl ≠ benzyl) because of the unique conformation assumed by the benzyl substituent. The rate of the base-catalyzed reaction depends on the extent of hindrance about the nitrogen atom of the tertiary amine as well as on its basicity. The data suggest that the relative rates of racemization of oxazolones are not a true reflection of the relative tendencies to racemize of the pertinent residues during couplings of the parent acids.

scholarly journals Synthesis of new series of Pyrazoline, and study their Kinetics and Reaction Mechanism

2019 ◽  
Vol 7 (2) ◽  
pp. 5-13
Author(s):  
Kosrat N. Kaka ◽  
Salam G. Taher ◽  
Wali M. Hamad ◽  
Aram H. Ibrahim
Keyword(s):  
Free Energy ◽  
Reaction Mechanism ◽  
Thermodynamic Parameters ◽  
Compensation Effect ◽  
New Products ◽  
Order Reaction ◽  
Membered Ring ◽  
Free Energies ◽  
First Order ◽  
Kinetics Of

A new series of novel pyrazoline compounds were synthesized by addition of thiosemicarbazide to the 2,6-dibenzylidenecyclohexanone (Chalcone) and its para substituted derivatives. This study was conducted for four purposes. Firstly, a series of five membered ring pyrazoline compounds were synthesized and the structure of all new products obtained are supported by spectral data (1H-NMR, 13CNMR, IR and UV-Vis.), and the effect of substituents were studied. Secondly, the reaction kinetics of the new synthesized compounds were studied to investigate the reaction mechanism pathway and order of the reaction; it was found that, the reaction undergoes via Claisen route of mechanism with first-order reaction. Thirdly, the thermodynamics of the reaction were studied, the rate of the reaction, Arrhenius parameters (A), and thermodynamic parameters for activation includes (free energies (Ea), entropies (ΔS#), and Gibbs free energy (ΔG#) were estimated. Finally, the compensation effect was also studied, and found the same pathway for all of the synthesized pyrazoline compounds.

Kinetics and Mechanism of Oxidation of Tin(II) by Hexachloroiridate(IV) in Aqueous Perchlorate Solutions

1992 ◽  
Vol 57 (2) ◽  
pp. 326-331 ◽  
Author(s):  
Refat M. Hassan
Keyword(s):  
Reaction Mechanism ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
First Order ◽  
Mechanism Of Oxidation ◽  
Kinetics Of ◽  
Overall Kinetics

The kinetics of hexachloroiridate(IV) oxidation of tin(II) in aqueous perchlorate media at a constant ionic strength of 2.0 mol dm-3 have been studied spectrophotometrically. The reaction was found to follow second-order overall kinetics and first order with respect to each of the reactants. The results showed hydrogen ion dependence where the reaction rate increased with increasing hydrogen ion concentration. The activation parameters were evaluated and a tentative reaction mechanism has been discussed.

Formation of hexacyanomanganate(II) in cyanide medium and kinetics and mechanism of its oxidation by chromate

1989 ◽  
Vol 67 (2) ◽  
pp. 279-283
Author(s):  
Guillermo López-Cueto ◽  
Mlguel Duarte
Keyword(s):  
Reaction Mechanism ◽  
Complex Formation ◽  
Rate Constant ◽  
Equilibrium Constants ◽  
Formation Rate ◽  
Experimental Results ◽  
First Order ◽  
Hydroxo Complexes ◽  
Monomolecular Decomposition ◽  
Kinetics Of

The rate of formation of hexacyanomanganate(II) is first-order in Mn(II) and depends on both the cyanide and hydroxide concentrations. The experimental results agree with a reaction mechanism which involves manganese(II) cyano- and hydroxo-complexes. Chromate slowly oxidizes hexacyanomanganate(II). The kinetics of this reaction is first-order on hexacyanomanganate(II), and the experimental rate constant depends on the chromate concentration according to the equation kexp = 3kK[Cr(VI)]/(1 + K[Cr(VI)]). The effect of both the CN− and the OH− ions is slighter. A tentative mechanism is proposed which involves a pre-equilibrium with the formation of a hexacyanomanganate(II)–chromate complex, followed by a monomolecular decomposition. By comparing this reaction mechanism with that of other one-electron chromate reductions, it appears that hexacyanomanganate(II) behaves like octacyanomolybdate(IV) rather than like hexacyanoferrate(II) and other substitution-inert reductants. Both the equilibrium constants for the complex formation and the rate constant for its decomposition are evaluated, and voltammetric evidence of the formation of hexacyanomanganate(III)–chromate complexes is also presented. Keywords: hexacyanomanganate(II), formation rate, oxidation with chromate, kinetics, mechanism.

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