ChemInform Abstract: MENSCHUTKIN REACTION OF TRIETHYLAMINE AND OF PYRIDINE WITH METHYL IODIDE. ACTIVATION ENTHALPY VERSUS ACTIVATION ENTROPY CORRELATIONS AND EXTENDED BROENSTED TREATMENTS IN ACETONITRILE-METHANOL MIXTURES

1985 ◽  
Vol 16 (14) ◽  
Author(s):  
Y. KONDO ◽  
M. OGASA ◽  
S. KUSABAYASHI
Keyword(s):  
Methyl Iodide ◽  
Activation Enthalpy ◽  
Activation Entropy

Significance test of refractive index of solvent in evaluation of effect of medium on rates of quaternization reactions of methyl iodide with amines

1990 ◽  
Vol 55 (1) ◽  
pp. 180-184 ◽  
Author(s):  
Taťjana Nevěčná ◽  
Vojtěch Bekárek
Keyword(s):  
Refractive Index ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Relative Permittivity ◽  
Significant Contribution ◽  
Activation Enthalpy ◽  
Dipole Moments ◽  
Significance Test ◽  
Activation Entropy ◽  
Aprotic Solvents

The rate constants have been measured of the reactions of methyl iodide with triethylamine (I) and tributylamine (III) at 293 K in twelve aprotic solvents, methyl iodide with tripropylamine (II) at 293, 313, 323, and 333 K in fifteen solvents differing greatly in their dipole moments, relative permittivities, and refractive indexes, and diiodomethane with tripropylamine in diiodomethane at 293 K (k1 = 2.1 10-5 s-1). The aprotic solvents predominantly affect the activation entropy which for the reaction of II varies from -200 J mol-1 s-1 (in cyclohexane) to -108 J mol-1 s-1 (in diiodomethane). The activation enthalpy of the reaction of methyl iodide with tripropylamine (II) is only little affected by aprotic solvents, a significant increase in activation enthalpy has been observed in the case of amphiprotic solvents. The evaluation of effect of medium on the rate constants of the above-mentioned reactions by means of the Kirkwood functions of relative permittivity and refractive index has shown a significant contribution of the refractive index of solvent which is comparable with the effect of relative permittivity.

Kinetic Studies on the Polymerization of Dicyclohexylmethylmethane-4,4'-Diisocyanate with Polyoxytetramethylene Diol

2013 ◽  
Vol 791-793 ◽  
pp. 32-35
Author(s):  
Jian Cheng Wang
Keyword(s):  
Rate Constant ◽  
Arrhenius Equation ◽  
Activation Enthalpy ◽  
Kinetic Studies ◽  
Activation Entropy ◽  
Dimethyl Acetamide ◽  
Different Temperatures ◽  
Ft Ir ◽  
Temperature Activation

Dicyclohexylmethylmethane-4,4'-diisocyanate is used to react with polyoxytetramethylene diol at different temperatures. N,N-Dimethyl acetamide is used as solvent.In situFT-IR is used to monitor the reaction to work out rate constant, Arrhenius equation and Eyring equation. The polymerization has been found to be a second order reaction, and the rate constant increases with the rise of temperature. Activation energy (Ea), activation enthalpy (ΔH) and activation entropy (ΔS) for the polymerization are respectively calculated out, which are very useful to reveal the reaction mechanism.

The Thermal Dependence of Flagellar Activity in Strigomonas Oncopelti

1965 ◽  
Vol 42 (3) ◽  
pp. 537-544
Author(s):  
M. E. J. HOLWILL ◽  
N. R. SILVESTER
Keyword(s):  
Activation Enthalpy ◽  
Beat Frequency ◽  
Published Data ◽  
Activation Entropy ◽  
Present Value ◽  
Kcal Mole ◽  
Thermal Dependence ◽  
Flagellar Beat ◽  
Rate Limiting

The flagellar beat frequency of Strigomonas oncopelti was found by cinémicrophotography at temperatures in the range 4-45° C. The thermal dependence is described by an activation enthalpy (ΔH‡) of 15.4 kcal./mole and an activation entropy (ΔS‡ of -1 e.u. ΔH‡ is comparable with published data on cilia and glycerol-extracted sperm. Values of ΔS‡ (-20 e.u.) deduced from the literature suggest a rate-limiting reaction between ions of like charge although the present value does not support this idea.

A Study of Effects of Temperature and Medium on Reaction of Triethylamine with Ethyl Bromide

1994 ◽  
Vol 59 (6) ◽  
pp. 1384-1391 ◽  
Author(s):  
Taťjana Nevěčná ◽  
Vojtěch Bekárek ◽  
Oldřich Pytela
Keyword(s):  
Activation Enthalpy ◽  
Solvent Polarity ◽  
Correlation Equation ◽  
Ethyl Bromide ◽  
Activation Entropy ◽  
Thermodynamic Quantities ◽  
Isokinetic Relationship ◽  
Complex Evaluation ◽  
Effects Of Temperature ◽  
The Individual

The rate constants of reaction of triethylamine with ethyl bromide have been measured in 13 solvents at the temperatures of 293, 313, 333, and 373 K. The activation entropies in the individual solvents increase when going from nonpolar to dipolar aprotic and polar protic solvents, which is explained by dominant solvation of the basic triethylamine and by formation of highly ordered associates without solvent in the activated complex in nonpolar solvent media. No isokinetic relationship has been found between the activation entropy and activation enthalpy, which indicates different solvent effects on the two quantities. The activation enthalpy and entropy of the reaction investigated are close to those of the reaction of triethylamine with ethyl iodide. Three methods have been used to evaluate the effect of medium at all the temperatures, their success being decreased in the order: Pytela's method - Kamlet-Taft - Koppel-Palm. Irrespective of the temperature, all the methods indicate that the reaction is accelerated by the solvent polarity, the significance of other effects being reflected differently depending on the temperature and the correlation equation used. A complex evaluation involving also the interpretation of the entropy and enthalpy components by means of empiric solvent parameters has shown that the resulting Gibbs energy represents a superposition of different effects of solvents on the two thermodynamic quantities, the solvent effect upon the activation entropy being predominant at the higher temperatures.

Chalcogen Interdiffusion in the System Pb(S, Se)

1979 ◽  
Vol 34 (1) ◽  
pp. 89-95 ◽  
Author(s):  
Volkmar Leute ◽  
Harald Böttner ◽  
Heinrich Schmidtke
Keyword(s):  
Interdiffusion Coefficient ◽  
Electron Microprobe ◽  
Mass Fraction ◽  
Activation Enthalpy ◽  
Solidus Temperature ◽  
Selenium Concentration ◽  
Activation Entropy ◽  
Concentration Profiles ◽  
Deviation From Stoichiometry

Abstract From the sulfur-and selenium-concentration profiles recorded by an electron microprobe the chalcogen interdiffusion coefficient of the system Pb(S, Se) is determined as a function of mass fraction cPbse and temperature. Undoped crystals and Pb-or chalcogen-saturated crystals are studied. The dependence of the interdiffusion coefficient on the deviation from stoichiometry shows that in the chalcogen-saturated part of the system the calcogen interdiffusion proceeds via chalcogen interstitials, whereas in the Pb-saturated part of the system the chalcogens diffuse via chalcogen vacancies. For pure PbSe it is shown that these vacancies are doubly ionized. The activation entropy of the diffusion of the chalcogens depends linearly on the ratio of activation enthalpy to solidus temperature.

The Ritter reaction of the acrylonitrile oligomer

1980 ◽  
Vol 45 (7) ◽  
pp. 1928-1936 ◽  
Author(s):  
Václav Janout ◽  
Pavel Čefelín
Keyword(s):  
Functional Group ◽  
Conformational Equilibrium ◽  
Activation Enthalpy ◽  
Butyl Alcohol ◽  
Ritter Reaction ◽  
Activation Entropy ◽  
Tert Butyl Alcohol ◽  
Entropy Parameter ◽  
The Ritter Reaction ◽  
Poly Acrylonitrile

The Ritter reaction of oligomeric models of poly(acrylonitrile) with tert-butyl alcohol in tetramethylene sulphone leads to the respective N-tert-butylamides and proceeds via the second-order kinetics. The rate constants increase only little on passing from the monomeric to the trimeric model. The decrease in the activation enthalpy ΔH is almost compensated for by the decrease in the activation entropy parameter. No effect of the neighbouring functional group on the reaction kinetics could be observed. A new conformational equilibrium is established during the reaction.

scholarly journals Oxidative addition of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)]: an experimental and computational study

2012 ◽  
Vol 10 (1) ◽  
pp. 256-266 ◽  
Author(s):  
Johannes Erasmus ◽  
Jeanet Conradie
Keyword(s):  
Methyl Iodide ◽  
Density Functional ◽  
Computational Study ◽  
Oxidative Addition ◽  
Activation Entropy ◽  
Apical Position ◽  
Strong Electron ◽  
Co Insertion ◽  
Experimental Values ◽  
Electron Donation

AbstractThe reaction rate of the oxidative addition and CO insertion steps of methyl iodide with [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)] are presented. Large negative experimental values for the activation entropy and results from a density functional theory computational chemistry study indicated trans addition of the CH3I to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)]. A study of the molecular orbitals gives insight into the flow of electrons during the oxidative addition reaction. CO insertion leads to a square pyramidal [Rh(PhCOCHCOPh)(P(OCH2)3CCH3)(COCH3)(I)] acyl product with the COCH3 moiety in the apical position. The strong electron donation of the P(OCH2)3CCH3 ligand accelerates the oxidation addition step of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)] by ca. 265 times faster (at 35°C) than that of the Monsanto catalyst, but inhibits the CO insertion step.

scholarly journals Thermal decomposition of 3,6-diphenyl-1,2,4,5-tetroxane in nitromethane solution

2018 ◽  
Vol 15 (2) ◽  
pp. 6306-6310
Author(s):  
Nelly Lidia Jorge ◽  
Alexander German Bordón ◽  
Andrea Natalia Pila ◽  
Mariela Ines Profeta ◽  
Maria Josefa Jorge ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Benzoic Acid ◽  
Activation Enthalpy ◽  
Decomposition Reaction ◽  
Activation Entropy ◽  
Order Kinetic ◽  
Stepwise Mechanism ◽  
First Order ◽  
Mechanism Of Decomposition ◽  
Organic Products

The thermal decomposition reaction of benzaldehyde diperoxide (DFT; 0.001 mol L-1) in nitromethane solution studied in the temperature range of 130.0-166.0 °C, follows a first-order kinetic law up to at least 60% DFT conversion. The organic products observed were benzaldheyde and benzoic acid. A stepwise mechanism of decomposition was proposed where the first step is the homolytic unimolecular rupture of the O-O bond. The activation enthalpy and activation entropy for DFT in nitromethane were calculated (DH# = 106.3 ± 1.0 kJ mol-1 and DS# = -58.6 ± 1.1 J mol-1K-1) and compared with those obtained in other solvents to evaluate the solvent effect.

scholarly journals Frustrated Lewis Pair Stabilized Phosphoryl Nitride (NPO), a Mono Phosphorus Analogue of Nitrous Oxide (N2O)

2021 ◽  
Author(s):  
André Eckhardt ◽  
Martin-Louis Riu ◽  
Peter Müller ◽  
Christopher Cummins
Keyword(s):  
Nitrous Oxide ◽  
Half Life ◽  
Negative Charge ◽  
Activation Enthalpy ◽  
Activation Entropy ◽  
Order Kinetic ◽  
Reactive Intermediate ◽  
First Order ◽  
Frustrated Lewis Pair ◽  
Good Agreement

Phosphoryl nitride (NPO) is a highly reactive intermediate, and its chemistry has only been explored under matrix isolation conditions so far. Here we report the synthesis of an anthracene (A) and phosphoryl azide-based molecule (N3P(O)A) that acts as a molecular synthon of NPO. Experimentally, N3P(O)A dissociates thermally with a first order kinetic half-life that is associated with an activation enthalpy of ΔH⧧ = 27.5 ± 0.3 kcal mol–1 and an activation entropy of ΔS⧧ = 10.6 ± 0.3 cal mol–1 K–1 that are in good agreement with calculated DLPNO-CCSD(T)/cc-pVTZ//PBE0-D3(BJ)/cc-pVTZ energies. In solution N3P(O)A undergoes Staudinger reactivity with tricyclohexylphosphine (PCy3) and subsequent complexation with tris(pentafluorophenyl)borane (B(C6F5)3, BCF) to form Cy3P-NP(A)O-B(C6F5)3. Anthracene is cleaved off photochemically to form the frustrated Lewis pair (FLP) stabilized NPO complex Cy3P⊕-N=P-O-B⊖(C6F5)3. Intrinsic Bond Orbital (IBO) analysis suggests that the adduct is zwitterionic, with a positive and negative charge localized on the complexing Cy3P and BCF, respectively.

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