Insertion Reaction Mechanism Research Articles

Density functional theory calculation on the C-H bond insertion reaction of dibromocarbene with acetaldehyde

The insertion reaction mechanism of CBr2 with CH3CHO has been studied by using the B3LYP/6-31G(d) method. The geometries of reactions, transition state and products were completely optimized. All the energy of the species was obtained at the CCSD(T)/6-31G(d) level. All the transition state is verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show that the propionaldehyde (HP1) is the main product of CH2 insertion with CH3CHO. The calculated results indicated that all the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CBr2 not only can insert the Cα-H [reaction I(1)]) but also can react with Cβ-H [reaction II(1)]. The statistical thermodynamics and Eyring transition state theory with Wigner correction are used to study the thermodynamic and kinetic characters of I(1) and II(1) in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature rang is 250 to 1750 K and 250 to 1600 K at 1.0 atm for I(1) and II(1) respectively. The rate constant and equilibrium constant are distinct in the range from 250 to 1000 K so that I(1) more easily occurs, while the reactions are not selected in the temperature range of 1000–1600 K.

Density functional theory study on the insertion reaction mechanism of dibromocarbene with formaldehyde

The insertion reaction mechanism of CBr2 with CH3CH2O has been studied by using the B3LYP/6-311G(d) and CCSD(T)/6-311G(d) at single point. The geometries of reactions, transition state and products were completely optimized. All the transition state is verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show that reaction (1) is the dominant reaction path, which proceeds via two steps: i) two reactants form an intermediate (IM1), which is an exothermal reaction of 8.62 kJ·mol−1 without energy barrier; ii) P1 is obtained via the TS1 and the H-shift, in which the energy barrier is 44.53 kJ·mol−1. The statistical thermodynamics and Eyring transition state theory with Wigner correction are used to study the thermodynamic and kinetic characters of this reaction in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature ranges from 200 to 1900 K at 1.0 atm, in which the reaction has a bigger spontaneity capability, equilibrium constant (K) and higher rate constant (k).

Theoretical study on the temperature influences on the insertion reactions of singlet phosphinidenes XP(X=H, Li, F, Cl, OH, SH) with polar hydrogen chloride

The insertion reaction mechanism of singlet phosphinidenes XP (X=H, Li, F, Cl, OH, SH) with polar hydrogen chloride molecule has been investigated at B3LYP/6-311+G(d, p) level in order to better understand their reactivity. Furthermore, the general statistical thermodynamics and Eyring transition state theory with Wigner correction were used to examine the temperature influences on the thermodynamic and kinetic properties of these reaction channels during the temperature range of 200–1000 K. It is concluded that with the rise of the temperature, the reaction equilibrium constant K decreases sharply, while the reaction rate constant k increases slowly for all these insertion reactions, and the reaction channel of LiP with HCl has both thermodynamic and kinetic advantages comparing with other concerned reactions, especially at high temperature.

Evidence of carbon–carbon bond formation on GaAs(100)via Fischer–Tropsch methylene insertion reaction mechanism

Sequential multiple methylene (CH2) insertions into adsorbed methyl species on clean gallium-rich GaAs(100)-(4 x 1) occurs to form higher alkenes (ethene, propene, butene) and two higher alkyl iodides (iodoethane, iodopropane), not reported for a semiconductor surface previously.

Dissociative adsorption and thermal desorption of dibromoethylene on Si(1 0 0)2 × 1: surface mediated dehalogenation and recombinative evolution of HBr

The room-temperature (RT) adsorption of dibromoethylene on Si(1 0 0)2 × 1 has been investigated by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) mass spectrometry. The C 1s and Br 3d XPS spectra indicate the presence of a mono-σ bonded vinyl bromide adspecies (30%) and a di-σ bonded vinylene adspecies (70%) on Si(1 0 0)2 × 1, which suggests dehalogenation of dibromoethylene producing one or both Br atoms upon RT adsorption. Annealing the sample to 645 K for 30 min completely removes the vinyl bromide adspecies, leaving behind the di-σ bonded vinylene. Recombinative desorption of HBr from the 2 × 1 surface has been observed over the temperature range 800–1000 K upon further annealing. The adsorption and desorption behaviour of dibromoethylene on Si(1 0 0)2 × 1 is found to be consistent with an insertion reaction mechanism, in marked contrast to the cycloaddition reaction mechanism observed for ethylene or acetylene on Si(1 0 0)2 × 1. The present work illustrates the surprisingly rich chemical activity of the 2 × 1 surface in facilitating dehalogenation of prototypical halogenated alkenes.

Asymmetric synthesis of cis-5-tert-butylproline with metal carbenoid NH insertion.

The highly stereoselective intramolecular metal carbenoid insertion reaction of sulfinimine-derived delta-amino alpha-diazoesters is used to prepare cis-5-tert-butylproline. A concerted or nearly concerted metal carbenoid N-H insertion reaction mechanism is proposed.

The Insertion Mechanism of Lithium into Mg2Si Anode Material for Li‐Ion Batteries

The reaction mechanism of lithium insertion into was studied using various analytic techniques including electrochemical measurements, X‐ray diffraction (XRD), and Auger electron spectroscopy (AES). Electrochemical tests demonstrated that 1 mol reacted with 3.9 mol Li from which the initial capacity obtained was approximately 1370 mAh/g. Ex situ XRD and AES data showed that lithium intercalated into the lattice first followed by alloying with Si and Mg. The degradation mechanism of during cycling was investigated because the materials degraded rapidly within ten cycles. The electrode material disintegrated and Li remained within the active material after ten cycles. The XRD and scanning electron microscope data suggested that the degradation mechanism of was due to the volume change during the alloying/dealloying reaction, and the volume expansion/contraction made the electrode materials electrically isolated. © 1999 The Electrochemical Society. All rights reserved.

Ion- and Electron-Transport Properties of a Single Particle of Disordered Carbon during the Lithium Insertion Reaction

The electrical dc conductance (S) and the solid-state diffusion coefficient of the lithium ion (DLi+) were evaluated for a single spherical particle of mesocarbon microbead (MCMB) heat-treated at 1000 °C. The measurements were conducted in situ during the electrochemical lithium insertion into the MCMB by using microelectrode-based techniques. The data obtained are discussed as functions of the electrode potential and of the amount of inserted lithium. Both parameters (S and DLi+) were found to depend on the lithium content, and their variation manner changed around 0.6 V vs Li/Li+ at which the inserted lithium amount was ca. 25% of the total insertion. The results would arise from the difference between the first and the second half of the lithium insertion reaction mechanisms.

Discussion on permeation transients in terms of insertion reaction mechanism and kinetics

The aim of this paper is to discuss the theoretical expressions for permeation transients in terms of the insertion reaction mechanism (one-step or two-step mechanism) and kinetics. The concentration and flux step boundary conditions are first discussed for potentiostatic charging. The intermediate case of decreasing input flux is also dealt with. On the other hand, constant flux or increasing flux can be envisaged under galvanostatic charging conditions. In contrast, the constant concentration boundary condition implicitly used in many galvanostatic permeation studies is incorrect if hydrogen saturation is disregarded. The diffusion coefficient of hydrogen in palladium, determined by different authors from permeation studies and electrochemical impedance spectroscopy (EIS) data, is finally discussed based on the insertion reaction mechanism and kinetics.

Reactions of Laser-Ablated Boron Atoms with Ethylene and Ethane. Infrared Spectra and DFT Calculations for Several Novel BC2Hx (x = 1, 2, 3, 4, 5) Molecules

Laser-ablated boron atoms have been reacted with ethylene during condensation in excess argon. The BC2H3 closed-shell isomers borirene (CH)2BH, ethynylborane H2BCCH, and borallene HBCCH2 have been identified from infrared spectra by using 10B, 13C, and D substitution and BP86/6-311G* isotopic frequency calculations. The observation of both cyclic aromatic and aliphatic products suggests that the reaction proceeds through both exothermic CC addition and C−H insertion reaction mechanisms. Evidence is presented for the most stable BC2H4 radicals, namely, and aliphatic H2BCCH2, which require H-atom migration within the intermediates first formed. Ethane gave a smaller yield of the same products, including linear HBCC and BCCH, vinylborane H2BC2H3, and an enhanced yield of the C−C insertion product CH3BCH2.

Investigations into the steric influences on the reaction mechanism of carbon dioxide insertion into metal-oxygen bonds. Carbonyl sulfide activation as a model for CO2

Steric influences on the insertion of CO 2 into metal-oxygen bonds have been investigated. The compounds [Et 4 N][W(CO) 5 O-2,6-Ph 2 -C 6 H 3 ] and [Et 4 N][W(CO) 4 (PPh 2 Me)OPh] have been synthesized and their reactivites toward CO 2 studied. The anion demonstrated a retarded rate of reaction with CO 2 as compared to the parent complex, [Et 4 N][W(CO) 5 OPh], a result ascribed to the steric bulk of the cis phosphine ligand

Some alkyl olefin cobalt complexes and their reactions with olefins

The complexes [Co(C 5Me 4Et)LMe 2] (I, L  C 2H 4; II, L  C 3H 6; III, L  Ph 3P) are reported, which undergo reactions with olefins. Following olefin exchange, I and II react with C 2H 3R giving [Co(C 5Me 4Et) (C 2H 3R) 2], CH 4 and CH 2 CMER (R  H or Me). The strong stereochemical specificity, together with deuteration experiments and 1H NMR spectrum of the reaction mixture all point to a simple olefin insertion reaction mechanism. Variable temperature 1H NMR shows olefin rotation in I.