Neue Bi(cyclopropylidene) durch CuCl2-katalysierte ‘Carben-Dimerisieiung’ von 1-Bromo-1-lithiocyclopropanen

New Bi(cyclopropylidenes) by CuCl₂-Induced ‘Carbene Dimerization’ of 1-Bromo-1-lithiocycIopropanes A series of so far unknown bi(cyclopropylidenes) 5 are prepared in a simple one-pot reaction by halogenolithio exchange between 1,1-dibromocyclopropanes 1a – c as well as 1e – i and BuLi at ?95°, to give 1-bromo-1-lithiocyclopropanes 2a – c as well as 2e – i , followed by treatment with CuCl₂ at low temperature and a simple workup at room temperature (Table 1). The influence of reaction parameters on yields of 5 (Tables 2, 4, and 5) and diastereoselectivity of the reaction 2 → 5 (Table 3) are discussed. In view of an elucidation of the reaction mechanism, first kinetic experiments of the quantitative reaction 1c → 2c → 5c are reported.     

Kinetics of the exothermic decomposition of 1-nitro-3-(β,β,β-trinitroethyl)-4,5-dinitroiminoimidazolidine-2-one

The kinetic parameters of the exothermic decomposition of the title compound in a temperatureprogrammed mode have been studied by means of DSC. The DSC data obtained are fitted to the integral, differential, and exothermic rate equations by the linear least-squares, iterative, combined dichotomous, and least-squares methods, respectively. After establishing the most probable general expression of differential and integral mechanism functions by the logical choice method, the corresponding values of the apparent activation energy (E _a), preexponential factor (A), and reaction order (n) are obtained by the exothermic rate equation. The results show that the empirical kinetic model function in differential form and the values of E _a and A of this reaction are (1 − α)^−4.08, 149.95 kJ mol⁻¹, and 10^14.06 s⁻¹, respectively. With the help of the heating rate and kinetic parameters obtained, the kinetic equation of the exothermic decomposition of the title compound is proposed. The critical temperature of thermal explosion of the compound is 155.71°C. The above-mentioned kinetic parameters are quite useful for analyzing and evaluating the stability and thermal explosion rule of the title compound. The text was submitted by the authors in English.     

Electrophilic aromatic substitution. 14. [1] A kinetic,NMR, and Raman study of the aluminum chloride-catalyzed reaction of p-toluene-sulfonyl chloride with benzene and toluene in dichloromethane

Vacuum line kinetic studies of the reaction of p-toluenesulfonyl chloride and benzene or toluene, using aluminum chloride as the catalyst and dichloromethane as the solvent were determined at 25°C by means of gas chromatography. The reaction is first-order in arene, tosyl chloride, and in AlCl₃ as catalyst. Noncompetitive results are k_T/k_B=22±7 with a product sulfone isomer distribution: ortho, 14±1%; meta, 4.3±0.2%; and para 82±1%. With hexadeuteriobenzene k_H/k_D was determined to be 1.8±0.1. Rate constant ratios and product isomer distributions were also determined competitively: with AlCl₃, k_T/k_B=30±2; % ortho, 13±1; % meta, 4.0±0.5; % para, 84±3; with SbCl₅, k_T/k_B=40±4; % ortho 10.3±0.4; % meta, 4.7±0.2; and % para, 85.0±0.5. The k_T/k_B ratio for AlCl₃ and the meta sulfone product percentages for both AlCl₃ and SbCl₅ are considerably higher than those reported in the literature. NMR and Raman studies suggest a molecular complex between p-tosyl chloride and AlCl₃, with coordination through oxygen as the dominant species and the probable electrophile in CH₂Cl₂. A reaction mechanism consistent with the kinetic and spectroscopic results is proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 367–372,1998     

Kinetics and mechanism of the autoxidation of pentaerythrityl tetraheptanoate at 180–220°C

A kinetic and mechanistic study of the autoxidation of liquid pentaerythrityl tetraheptanoate (PETH) at 180–220°C has been carried out utilizing a stirred-flow reactor. The results are consistent with the occurrence of a chain reaction scheme similar to that proposed for n-hexadecane autoxidation, namely, the formation of monohydroperoxides by the intermolecular abstraction reaction (3), the formation of α,γ- and α,δ-dihydroperoxides and α,γ- and α,δ-hydroperoxyketones by intramolecular peroxy radical abstraction reactions (4) and (4*), the bimolecular termination of peroxy radicals, reaction (6), and the rapid conversion of α,γ-hydroperoxyketones to the corresponding cleavage acids and methyl ketones, reaction (7). Comparisons of various rate parameters for the n-hexadecane and PETH systems reveal that the values of k₇ and (k₃/H atom)/(2 k₆)^1/2 are within experimental uncertainties identical for the two systems at 180°C. The proposed reaction scheme includes the concurrent formation of hydroxy radicals and hydroperoxyketone species. The results of kinetic analysis and the experimentally observed isomer distributions of primary and secondary monohydroperoxide products at high and low oxygen pressures suggest that ≈60% of the hydrogen abstractions from PETH at high oxygen pressures occur by hydroxy radicals.     

Catalytic Asymmetric Synthesis of the anti-COVID-19 Drug Remdesivir

The catalytic asymmetric synthesis of the anti-COVID-19 drug Remdesivir has been realized by the coupling of the P-racemic phosphoryl chloride with protected nucleoside GS441524. The chiral bicyclic imidazole catalyst used is crucial for the dynamic kinetic asymmetric transformation (DyKAT) to proceed smoothly with high reactivity and excellent stereoselectivity (96 % conv., 22:1 S_P:R_P). Mechanistic studies showed that this DyKAT is a first-order visual kinetic reaction dependent on the catalyst concentration. The unique chiral bicyclic imidazole skeleton and carbamate substituent of the catalyst are both required for the racemization process, involving the phosphoryl chloride, and subsequent stereodiscriminating step. A 10 gram scale reaction was also conducted with comparably excellent results, showing its potential for industrial application.     

Dediazoniation of Arenediazonium Ions in Homogeneous Solutions. Part XVII. Kinetics and mechanisms of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate in weakly alkaline aqueous solutions in the presence of oxygen

The kinetics of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate have been studied in buffer solutions in the pH-range 9.0–10.0, ionic strength I = 0.10, at 20.0° in glass and polytetrafluoroethylene vessels. The presence of oxygen (<5 ppb of O₂, 60 to 100 ppb of O₂, air, > 99% of O₂) has a decisive influence on the rate and kinetic order of the dediazoniation. Iodoacetic acid inhibits the reaction, whereas p-chlorophenol has a catalytic effect, and in air and >99% of O₂ it acts as an autocatalyst. The reaction is subject to general-base catalysis by water, hydroxyl ions, hydrogen carbonate and carbonate ions. The kinetic results are interpreted in conjunction with data concerning the reaction products [2] and a ¹⁵N-CIDNP. investigation of a related system [3]. Specific radical chain mechanisms are consistent with the results.     

Asymmetric Synthesis of 2,3‐Dihydropyrroles by Ring‐Opening/Cyclization of Cyclopropyl Ketones Using Primary Amines

The asymmetric ring‐opening/cyclization of cyclopropyl ketones with primary amine nucleophiles was catalyzed by a chiral N,N′‐dioxide/scandium(III) complex through a kinetic resolution process. A broad range of cyclopropyl ketones and primary amines are suitable substrates of this reaction. The corresponding products were afforded in excellent enantioselectivities and yields (up to 97 % ee and 98 % yield) under mild reaction conditions. This method provides a promising access to chiral 2,3‐dihydropyrroles as well as an effective procedure for the kinetic resolution of 2‐substituted cyclopropyl ketones.     

Reactions on polymers with amine groups. III. Description of the addition reaction of pyridine and imidazole compounds with α,β-unsaturated monocarboxylic acids

A detailed study of the synthesis of betaine products that result from addition reactions of poly (4-vinylpyridine) and poly (N-vinylimidazole) as well as of their model compounds, with α,β-unsaturated monocarboxylic acids is presented. A reaction mechanism based on experimental observations and proved by kinetic analysis is proposed. It consists of two reactions: the addition, which involves two molecules of acid and leads to X⁺B⁻-like structures, where the cation X⁺ results from the addition of the amino nitrogen to the double bond of acid and B⁻ is the carboxyl anion, and an equilibrium reaction between X⁺B⁻ and the betaine structure X^±. The latter occurs only in protic solvents and is coupled with the addition reaction. The process was especially investigated in methanol, because this solvent allows determination of the kinetic parameters. Some values of the addition rate constants are given. The study is based on ¹H-NMR measurements and observations. © 1996 John Wiley & Sons, Inc.     

Kinetic energy release during CO loss by rearrangement of α-benzoylcarbenium ions

Primary α-benzoylcarbenium ions (a) and tertiary α-benzoyldimethylcarbenium ions (b) are obtained by chemical ionization of ω-hydroxyacetophenone and its dimethyl derivative, respectively. Both α-acylcarbenium ions decompose by a rearrangement reaction and subsequent loss of a CO molecule. The kinetic energy released during this process by metastable ions a and b has been determined under different experimental conditions. The kinetic energy released during the CO elimination from the tertiary α-benzoyldimethylcarbenium ions b is independent of the experimental conditions and gives rise to dish-topped peaks with T₅₀=440±20 meV in the MIKE spectra of b. In contrast to this the kinetic energy releases and the peak-shapes in the MIKE spectra of the primary α-benzoylcarbenium ion a varies with the experimental conditions. The mechanism of this rearrangement reaction is discussed, and it is shown by a MNDO calculation of the heats of formation of the relevant ions that the different characteristics of the kinetic energy release during the fragmentation of primary and tertiary carbenium ions can be attributed to different types of reaction energy profiles.     

Free-radical homopolymerization and copolymerization of ethyl α-hydroxymethylacrylate in tetrahydrofuran

Ethyl α-hydroxymethylacrylate (EHMA) was polymerized in a 3 mol/L tetrahydrofuran solution at 50°C, using 2–2' azobisisobutyronitrile as initiator. The kinetic behavior indicates a higher polymerization rate for EHMA than for methyl methacrylate (MMA). Copolymerization reaction between MMA and EHMA, under the same experimental conditions, was carried out and values of r_MMA = 1.264 and r_EHMA = 1.285 were found for the reactivity ratios. The comparison of triad sequences as determined from Bernouillian statistic to those calculated from the experimental spliting of O-methyl and α-methyl ¹H-NMR signals of the copolymers confirm the obtained results. © 1992 John Wiley & Sons, Inc.     

Reaction Kinetics of the Hydroperoxide Epoxidation of 1-Octene in the Presence of Mo2B

The kinetics of epoxidation of 1-octene by tert-butyl hydroperoxide in the presence of molybdenum boride (Mo₂B) was studied. The effects of reactant and reaction product concentrations on the process were examined. A kinetic scheme was proposed, and the kinetic parameters of the process were calculated.     

The Kissinger law and the IKP method for evaluating the non-isothermal kinetic parameters

The following problems concerning the apparent compensation effect (CE) (lnA=a+bE, where A is the pre-exponential factor, E is the activation energy, a and b are CE parameters) due to the change of the conversion function and on which the invariant kinetic parameters method (IKP method) is based, are discussed: (1) the explanation of this kind of CE; (2) the choice of the set of conversion functions that checks CE relationship; (3) the dependencies of CE parameters on the heating rate and the temperature corresponding to the maximum reaction rate. Using the condition of maximum of the reaction rate suggested by Kissinger (Kissinger law), it is pointed out that, for a certain heating rate, the CE relationship is checked only for reaction order (Fn) and Avrami-Erofeev (An) kinetic models, and not for diffusion kinetic models (Dn). Consequently, IKP method, which is based on the supercorrelation relationship between CE parameters, can be applied only for the set Fn+ An of kinetic models. The dependencies of a and b parameters on the heating rate and T _m (temperature corresponding to maximum reaction rate) are derived. The theoretical results are discussed and checked for (a) TG simulated data for a single first order reaction; (b) TG data for PVC degradation; (b) the dehydration of CaC₂O₄·H₂O.     

Estimation of kinetic parameters of reversible chain reactions of quinoneimines with hydroquinones having self-acceleration periods

A new approach is suggested for determining the kinetic parameters and rate constants of the elementary steps of reversible chain reactions having self-acceleration periods due to the long time required for the concentrations of the chain-carrier radicals to reach their steady-state values. This approach is illustrated by the example of the reversible chain reaction between N,N′-diphenyl-1,4-benzoquinonediimine and 2,5-dichlorohydroquinone in chlorobenzene. The disappearance rate of one of the initial reactants, N,N′-diphenyl-1,4-benzoquinonediimine, at the inflection point of its disappearance curve, is considered as the basic kinetic characteristic of the reaction. The empirical function y = aexp(bt ^c ) + d, where a, b, c, and d are the fitted parameters (b < 0, c > 1), is suggested for approximating the S-shaped kinetic curves and for calculating the reaction rate. The rate constants of the elementary steps are preferably derived from experimental data obtained at equal concentrations of the initial reactants, and also product additions when their effect on the reaction rate is studied. The effective rate constant of chain termination is derived from the time to reach the steady state. The results obtained in this way are compared with earlier data obtained using the “initial” reaction rates calculated by means of exponential approximation of portions of N,N′-diphenyl-1,4-benzoquinonediimine disappearance curves after the inflection point.     

Kinetic study of hydroperoxide epoxidation of 1‐octene in the presence of molybdenum disilicide as a catalyst in a low concentration range of olefin

The kinetic regularities of the influence of low 1‐octene concentrations on its epoxidation by tert‐butyl hydroperoxide in the presence of molybdenum disilicide (MoSi₂) as a catalyst were investigated. The minimum in the dependence of the initial rate of hydroperoxide consumption on 1‐octene concentration was observed. The kinetic scheme of epoxidation, which includes the competition between hydroperoxide and olefin for the catalytic active centers, was proposed. The equation for the reaction rate was derived according to the kinetic scheme. The kinetic parameters of epoxidation were calculated. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 623–628, 2009     

1D Structure Sodium Coordination Anion based on [5‐(Dinitromethylene)‐4,5‐dihydro‐1H‐tetrazole]: Syntheses,Structures, and Thermal Behavior

The ten‐coordinate complex, (HATr)[Na(DNMz)] · H₂O ( 1 ) was synthesized by reaction of 5‐(dinitromethylene)‐4,5‐dihydro‐1H‐tetrazole (DNMz), sodium hydroxide, and 3‐hydrazinium‐4‐amino‐1,2,4‐1H‐triazolium dichloride (HATr) in aqueous solution and characterized by various physico‐chemical techniques. Complex 1 is an energetic material with a nitrogen content of 51.2 % and a decomposition temperature of 128.9 °C. The molecular structure of complex 1 crystallizes in the monoclinic system with P2(1)/c group and shows an infinite 1D chain structure. The heat of formation was determined as –122.27 kJ · mol^–1 by using bomb calorimetry. In addition, the kinetic parameters were studied by Kissinger's and Ozawa‐Doyle's methods.     

CuII‐Containing 1‐Aminocyclopropane Carboxylic Acid Oxidase Is an Efficient Stereospecific Diels–Alderase

In the context of developing ecofriendly chemistry, artificial enzymes are now considered as promising tools for synthesis. They are prepared in particular with the aim to catalyze reactions that are rarely, if ever, catalyzed by natural enzymes. We discovered that 1‐aminocyclopropane carboxylic acid oxidase reconstituted with Cu^II served as an efficient artificial Diels–Alderase. The kinetic parameters of the catalysis of the cycloaddition of cyclopentadiene and 2‐azachalcone were determined (K_M=230 μm , k_app=3 h^?1), which gave access to reaction conditions that provided quantitative yield and >99 % ee of the (1S,2R,3R,4R) product isomer. This unprecedented performance was rationalized by molecular modeling as only one docking pose of 2‐azachalcone was possible in the active site of the enzyme and this was the one that leads to the (1S,2R,3R,4R) product isomer.     

The reaction of hydrogen atoms with 1-butanethiol and thiolane the role of chemically activated 1-butanethiol

The reaction of 1-butanethiol with hydrogen atoms has been studied at temperatures of 295° and 576° K under the pressure of 660 Pa, using a conventional discharge-flow apparatus. The reaction products (besides hydrogen sulfide and methane) under the low conversion range (～10%) consisted mainly of n-butane, 1-butene, and propylene-propane, with the relative yields of 70, 25, and 5% at 295° K and 25, 50, and 10% at 576°K. Analysis of kinetic equations by numerical integration indicates that the following initial steps are consistent with the experimental results: where the following expressions have been derived for k₁ and k₂: The subsequent reaction of the butylthio radical with hydrogen atoms leads to the chemically activated 1-butanethiol which either stabilizes to 1-butanethiol or decomposes to 1-butene and hydrogen sulfide, depending on the experimental conditions. A similar analysis of the data on the thiolane-H system has yielded the following rate parameters for the initial step to form the 4-mercapto-1-butyl radical: .     

Thermal Behavior of N,N＇Bis[N-（2,2,2-trinitroethyl）-N-nitro]ethylenediamine

The thermal behavior and kinetic parameters of the exothermic decomposition reaction of N‐N‐bis[N‐(2,2,2‐tri‐nitroethyl)‐N‐nitro]ethylenediamine in a temperature‐programmed mode have been investigated by means of differential scanning calorimetry (DSC). The results show that kinetic model function in differential form, apparent activation energy E_a and pre‐exponential factor A of this reaction are 3(1 ‐α)^2/3, 203.67 kJ·mol^?1 and 10^20.61s^?1, respectively. The critical temperature of thermal explosion of the compound is 182.2 °C. The values of ΔS^≠ ΔH^≠ and ΔG^≠ of this reaction are 143.3 J·mol^?1·K^?1, 199.5 kJ·mol^?1 and 135.5 kJ·mol^?1, respectively.     

Enzymatic hydrolysis of protein: Mechanism and kinetic model

The bioreaction mechanism and kinetic behavior of protein enzymatic hydrolysis for preparing active peptides were investigated to model and characterize the enzymatic hydrolysis curves. Taking into account single-substrate hydrolysis, enzyme inactivation and substrate or product inhibition, the reaction mechanism could be deduced from a series of experimental results carried out in a stirred tank reactor at different substrate concentrations, enzyme concentrations and temperatures based on M-M equation. An exponential equation dh/dt = aexp(-bh) was also established, where parameters a and b have different expressions according to different reaction mechanisms, and different values for different reaction systems. For BSA-trypsin model system, the regressive results agree with the experimental data, i.e. the average relative error was only 4.73%, and the reaction constants were determined as K _m = 0.0748 g/L, K _s = 7.961 g/L, k _d = 9.358/min, k ₂ = 38.439/min, E _a = 64.826 kJ/mol, E _d = 80.031 kJ/mol in accordance with the proposed kinetic mode. The whole set of exponential kinetic equations can be used to model the bioreaction process of protein enzymatic hydrolysis, to calculate the thermodynamic and kinetic constants, and to optimize the operating parameters for bioreactor design. __________ Translated from Journal of Tianjin University, 2005, 38(9) (in Chinese)     

KINETICS,MEDIUM, AND DEUTERIUM ISOTOPE EFFECTS IN THE ALKALINE DECOMPOSITION OF QUATERNARY PHOSPHONIUM SALTS III1 Tetraphenylphosphonium Chloride in Dimethylsulphoxide-Water Mixtures

Abstract

The reaction between tetraphenylphosphonium chloride and hydroxide or deuteroxide anions was studied kinetically in a series of dimethylsulphoxide-water mixtures at several temperatures. The rate is first-order in the phosphonium cation and second-order in the hydroxide or deuteroxide anions. The reaction shows a dramatic increase in rate, up to about 10¹⁰ times, as the DMSO content is increased. The rate enhancement is attributed to a considerable drop in activation energy affected not only through an increased desolvation of reactant anions, but also through an increase in solvation of the transition state, brought about by gradual addition of DMSO. The kinetic solvent deuterium isotope effect in 60% DMSO-40% D₂O is strongly dependent on temperature. The rate constant in the latter solvent mixture is represented by k ⁱ = 11.9 e ^?12700/RT l ² mole^?2 sec^?1 as compared to k ⁱ = 19.0 e ^?22500/RT l ² mole^?2 sec^?1 in the corresponding 60% DMSO-H₂O mixture. The thermodynamic parameters of activation show strong dependence on solvent composition and are related to structural changes and solvation power of the reaction medium.