Infrared Kinetic Study of the Catalyzed and Uncatalyzed Reaction of Butanol-1 with α-NaphthyIisocyanate in Various Solvents

The condensation reaction of α-naphthylisocyanate with n-butanol has been studied in toluene and in bis(2-methoxyethyl) ether (diglyme) by IR spectroscopy at different temperatures (20–60°C). A kinetic study shows that it is first order with respect to each reactant even when the reaction is catalyzed by tin octoate. A general mathematical treatment indicates that secondary reactions may occur in some conditions of temperature, solvent and catalyst, but do not take place in our system. The activation enthalpy and entropy have been determined.     

The Reactions Between Halides and Alcohols in the Presence of Phase Transfer

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Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.     

Molecular Organization of Reagents in the Kinetics and Catalysis of Liquid-Phase Reactions: XI. Manifestation of the Structure of Solution in the Kinetics of Water Addition to Isocyanate in Water–Dioxane Mixtures

Evidence for the structural effect of liquids associated by hydrogen bonds on the kinetics of molecular reactions was experimentally found. The kinetics of hydrolysis of (phenylaza)phenyl isocyanate in water–dioxane mixtures was studied at various temperatures and in the presence of structure-making and structure-breaking additives. The apparent order of reaction with respect to water concentration increased with temperature because of the partial breaking of the H-bond solution structure. It was found that the value of was affected by salt additives, for which positive (Et₄NCl) or negative (KI) hydration is typical. This hydration resulted in strengthening or partially breaking the H-bond structure of water, respectively. It follows from the kinetic data that the addition of 0.1 mol/l Et₄NCl was equivalent to a decrease in the solution temperature by 6 to 7°, whereas the addition of 0.1 mol/l KI was equivalent to an increase in the temperature by 5 to 6°. The effect of poly(ethylene oxide) additives (which stabilize the structure of water) on the value of was similar to the effect of the tetraethylammonium salt, which is characterized by positive hydration.     

Analysis of the Kinetic Parameters of the Enzymatiс Catalysis of Esterifications in Hexane

Kinetics and Catalysis - Some of the kinetic parameters of esterifications of aliphatic acids and alcohols involving biocatalysts in nonaqueous media were analyzed using mathematical modeling. The...     

Theoretical Study on the Mechanisms and Kinetic Parameters for the Initiation Reaction of Grubbs–Hoveyda Catalyst

Russian Journal of Physical Chemistry A - In this work, typical alkenes and Grubbs–Hoveyda catalyst (Cat1) were selected to study the mechanism and kinetic parameters (the entropies,...     

Mechanism Equivalence in Enzyme–Substrate Reactions: Distributed Differential Delay in Enzyme Kinetics

We consider single enzyme–substrate reaction mechanisms involving multiple complexes and demonstrate that these are equivalent to a distributed delay system without complexes. The distribution of the delay is determined by the number of intermediates and the relative sizes of the rates of the individual reaction mechanisms. We also consider the limit where there are a large number of intermediate complexes, and the conditions under which a number of known reaction mechanisms are equivalent. The present formalism brings forth new perspectives in the implementation of experimental techniques to rule out particular reaction mechanisms by studying the distribution of the delay between reactant mixing and product formation.     

Manifestation of the Even–Odd Effect in the Spectral Properties of Solvated Electron and in the Probability of Positronium Formation in Alcohols

A change in the energy E _max of the solvated electron, which corresponds to the maximum intensity of its optical absorption spectrum in the homologous series of alcohols seems to be alternating in character. The effect is retained upon elevation of pressure up to 2 kbar but disappears in alcohols frozen at 77 K. Probably, the effect also holds for amines. The alternating character of variation is also observed for the intensity Y ₁ of the narrow components of the angular spectrum of -photons generated upon positron annihilation in alcohols and normal alkanes. The nature of alternation of E _max is associated with the mutual elimination of electric fields induced by the dipole moments of two neighboring CH₂ groups in each solvent molecule, including also the molecules forming the solvation shell of an excess electron. That fact that the E _max value correlates to Y ₁ led to the conclusion that Y ₁, rather than the intensity I ₃ of the long-lived component of the annihilation time spectrum generally used for the purpose, more adequately characterizes the positronium formation probability.     

Approach to the Determination of Kinetic Order of Catalyst Deactivation: Observation of Unusual Kinetics in the Suzuki – Miyaura Reaction

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Kinetics and Mechanism of the Hydrolysis of Benzyl Ether Bonds in Aqueous–Organic Media

Russian Journal of Physical Chemistry A - Kinetic parameters (rate constant, energy of activation, and entropy of activation) of the acid-catalyzed hydrolysis of the benzyl ethers...     

Kinetic analysis of the crystallization processes in the glasses of the Bi–As–S system

Kinetic analysis of the crystallization process in Bi₄(As₂S₃)₉₆ and Bi₆(As₂S₃)₉₄ glasses was performed based on DSC curves recorded under non-isothermal measurement conditions. Samples were thermally treated at different heating rates in the temperature range 300?C770?K. The activation energy of crystallization E and the pre-exponential factor K ₀ are determined by the Kissinger method and the characteristic crystallization parameters m and n of investigated glasses by the Matusita method. For both crystallization processes the glass with 4 at.% of Bi is characterized by the mechanism of volume nucleation, which is manifested in the form of two-dimensional growth at the first crystallization process, and as three-dimensional at the second one. On the other hand, in the sample with 6 at.% Bi, the average value of the parameter m is close to one, which indicates one-dimensional crystal growth. Compatibility of the values of the parameters m and n suggests that this sample has a large number of crystallization centers, which do not increase significantly during the thermal treatment.     

Anomalies in the Change of Volumetric Parameters of the Diels–Alder Reaction in Solution

In this article negative values of the activation volume in retro-Diels–Alder reactions are interpreted in terms of the different possibilities of penetration of the solvent molecules into the sterically branched structures of the adduct and activated complex. Empty spaces, inaccessible to penetration of solvent molecules, lead to increases of the molar volume of the screened adducts in solution and, consequently, to a less negative value of the Diels–Alder reaction volume. The values of partial molar volumes of anthracene, maleic anhydride and the adducts cyclopentadiene–maleic anhydride, anthracene–maleic anhydride and anthracene–tetracyanoethylene, in several solvents, were calculated from the solution density data.     

Photochemical Reactions in the Synthesis of Protein–Drug Conjugates

The ability to modify biologically active molecules such as antibodies with drug molecules, fluorophores or radionuclides is crucial in drug discovery and target identification. Classic chemistry used for protein functionalisation relies almost exclusively on thermochemically mediated reactions. Our recent experiments have begun to explore the use of photochemistry to effect rapid and efficient protein functionalisation. This article introduces some of the principles and objectives of using photochemically activated reagents for protein ligation. The concept of simultaneous photoradiosynthesis of radiolabelled antibodies for use in molecular imaging is introduced as a working example. Notably, the goal of producing functionalised proteins in the absence of pre-association (non-covalent ligand-protein binding) introduces requirements that are distinct from the more regular use of photoactive groups in photoaffinity labelling. With this in mind, the chemistry of thirteen different classes of photoactivatable reagents that react through the formation of intermediate carbenes, electrophiles, dienes, or radicals, is assessed.     

Molecular, Thermodynamic, and Kinetic Parameters of the Free Radical C2H5 · in the Gas Phase

The wave function, energy, equilibrium geometry, and normal vibration frequencies of the ground state of the free radical C₂H₅ ^· were obtained by ab initio calculations with inclusion of electron correlation effects at the UB3LYP/6-311++G^{* *} level. The resulting molecular parameters were used to estimate the thermodynamic functions of an ideal gas of C₂H₅ ^·. From the thermodynamic functions of C₂H₅ ^·, I^·, C₂H₅I, C₂H₄, and HI and the kinetic curves of isothermal pyrolysis of ethyl iodide, the absolute rate constants of elementary reactions of free ethyl radical and the mentioned iodine compounds were estimated. The dissociation energy E _{D , 0}(C₂H₅-I) and the standard formation enthalpy _f H ⁰298 (C₂H₅ ^·) were found.     

Kinetics of the Ziegler-Natta Polymerization of 1-Octene——The Kinetics and Mechanism of the Induction period

The kinetics of the induction period in the polymerization of 1-octene catalyzed by Solvay TiCl3-alkyl aluminium was studied with a dilatometer. The induction period decreases as [TiCl3] and [M]0 increase and temperature rises. It was observed through a microscope that large catalyst particles broke up into small particles in the induction period. So a kinetic model was proposed which ascribes the induction period to the breaking up of catalyst particles under the effect of polymer, and the most of the experimental results can be explained on the basis of the model.     

Kinetics and Thermodynamics of the Absorption of Hydrogen in β-titanium Alloys

A thermogravimetric method was applied to study the hydrogen uptake in the near-β-titanium alloy Ti 10 2 3 and the metastable β-titanium alloy Ti 21S. The tests were performed in H₂-He gas mixtures with various partial pressures of H₂ at temperatures between 600 and 800°C. Basic findings such as the decreasing solubility of H₂ with increasing temperature could be verified, and first information on the effects of surface conditions was gained. Thus, it could be shown that, despite the low atomic mass of hydrogen, thermogravimetry is an appropriate tool for investigation of the H₂/metal interactions of titanium alloys. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chemical Reactions of Surfactants with Acid–Base Dyes and Determination of Imidazolines in the Air of the Working Area

Reactions of acid–base monoazo dyes with polyamine surfactants were studied. The ratios of components in the resulting compounds were determined; the stability constants and molar absorptivities were calculated. A mechanism was proposed for the reaction of monoazo dyes with amine and imidazoline surfactants with the formation of macroheterocycles. Approaches to predicting analytical reactions between monoazo dyes and surfactants were substantiated. The dependence of the extraction of these compounds on the pH of the aqueous phase and the concentrations of NaCl and ethanol was studied. The optimal conditions for extraction separation were found, and a procedure was developed for the spectrophotometric determination of 1-(-hydroxyethyl)-2-heptadecenyl-2-imidazoline (Imidazoline 17) and 1,1"-bis(-hydroxyethyl)-2-heptadecenyl-2-imidazolonium chloride (Imidastat O) in the air of the working area using Methyl Orange as the reagent. The determination limits were 0.025 and 0.12 g/mL, respectively. A sampling procedure was developed for the determination of Imidazoline 17 and Imidastat O in the air with determination limits of 0.05 and 0.25 mg/m³, respectively, for sampling 15 L of air to 60% ethanol.     

Determination of Kinetic Parameters and Metal Ions in Urea-Urease System Based on the Biochemical Reaction Heat Induced Laser Beam Deflection

Reaction heat induced laser beam deflection is a new analytical method which came in tobeing in 1993', by probing the gradient of the refraction index which was induced byreaction heat with a laser probe beam, one can relate the laser beam deflection to theconcentration of the sample.In this paper, the method was used for the study of the kinetic process for ureaurease system. It is well known that urease catalyzes the hydrolysis of urea as follows fUreaseNHZCONHZ HZO~ CO2 2NH3 QThe pro…     

Kinetic patterns in the formation of nanosized manganese–manganese oxide systems

Transformations in nanosized manganese films are studied by means of optical spectroscopy, microscopy, and gravimetry at different film thicknesses (d = 4–108 nm) and temperatures of heat treatment (T = 373–673 K). It is found that the kinetic curves of conversion are satisfactorily described in the terms of linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference is measured for Mn and MnO films, and photo EMF is measured for Mn–MnO systems. An energy band diagram is constructed for Mn–MnO systems. A model for the thermal transformation of Mn films is proposed that includes stages of oxygen adsorption, the redistribution of charge carriers in the contact field of Mn–MnO, and manganese(II) oxide formation.