Reaction Of CH Research Articles

The cycloaddition reaction of ethylene and methane mediated by Ir+ to generate a half-sandwich structure IrHCp+

The cycloaddition reactions of methane and ethylene mediated by Ir+ have been designed and studied by the techniques of mass spectrometry in conjunction with theoretical calculations. Studies have shown that Ir+ can mediate the cycloaddition reaction of CH4 and two C2H4 to generate a half-sandwich structure IrHCp+ (Cp = η5-C5H5) including pentamethylcyclopentadienyl ligand by continuous dehydrogenation reaction with the forming of three C-C bonds and seven C-H bonds. The orbital analysis indicates the mechanism of the cyclization reaction to generation of pentamethylcyclopentadienyl ligand with odd number carbon atom depends on the overlap of π orbitals in -C2H2 and carbene, which is more difficult than the forming of cyclobutadiene ligand and benzene. This study may help to understand the reaction mechanism in the cycloaddition reactions of organic compounds, which will be useful to guide the rational design of new catalysts with tailored selectivity and increased efficiency.

Dry reforming reactions of CH4 over CeO2/MgO catalysts at high concentrations of H2S, and behavior of CO2 at the CeO2-MgO interface

High concentrations of H2S are contained in unused industrial gases and biomass gasification gases, necessitating catalysts which are robust in the presence of H2S to produce H2 from them. Pure CeO2 is known for its robustness, but rare earth oxide consumption should be reduced to improve sustainability. Herein, a stable dry reforming reaction is demonstrated over CeO2/MgO under reaction conditions of 2000 ppm H2S. A comparable catalytic activity to pure CeO2 was exhibited by 5 mol% CeO2/MgO despite its low loading of CeO2. Further, no carbon deposition or impurity phases were formed in the catalyst after an 8-h reaction. Transmission electron microscopy revealed that MgO stabilized the CeO2 nanoparticles under these reaction conditions. Also, kinetic analyses, infrared spectroscopy, and isotopic labeling studies suggested that the CeO2-MgO interface strongly captures CO2 and supplies it to the CeO2 surface to accelerate the dry reforming reaction.

Effect of B Site Substitution on the Catalytic Activity of La‐Based Perovskite for Oxidative Coupling of Methane

The effect of B site element in LaBO3(B = Al, Ga, In, Yb, Co, Mn, Fe) perovskites on the catalytic performance for the oxidative coupling of methane (OCM) reaction is investigated. Among the catalysts tested, LaAlO3, LaGaO3, LaInO3,and LaYbO3show higher activity for the formation of C2hydrocarbons in the OCM reaction. From the kinetic study on LaAlO3and LaCoO3, which are the highest and lowest active catalysts, the CH3• formation, as the first step in the OCM reaction, via the reaction of CH4with oxygen is strongly affected by the B site element. X‐ray photoelectron spectroscopy analysis and the16O/18O isotopic exchange reaction suggest that the role of the B site element in LaBO3perovskite is to create enough amount of surficial mobile oxygen species.

Aerobic photolysis of methylcobalamin: unraveling the photoreaction mechanism.

The photo-reactivity of cobalamins (Cbls) is influenced by the nature of axial ligands and the cofactor's environment. While the biologically active forms of Cbls with alkyl axial ligands, such as methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), are considered to be photolytically active, in contrast, the non-alkyl Cbls are photostable. In addition to these, the photolytic properties of Cbls can also be modulated in the presence of molecular oxygen, i.e., under aerobic conditions. Herein, the photoreaction of the MeCbl in the presence of oxygen has been explored using density functional theory (DFT) and time-dependent DFT (TD-DFT). The first stage of the aerobic photoreaction is the activation of the Co-C bond and the formation of the ligand field (LF) electronic state through the displacement of axial bonds. Once the photoreaction reaches the LF excited state, three processes can occur: namely the formation of OO-CH3 through the reaction of CH3 with molecular oxygen, de-activation of the {Im⋯[CoII(corrin)]⋯CH3}+ sub-system from the LF electronic state by changing the electronic configuration from (dyz)1(dz2)2 to (dyz)2(dz2)1 and the formation of the deactivation complex (DC) complex via the recombination of OO-CH3 species with the de-excited [CoII(corrin)] system. In the proposed mechanism, the deactivation of the [CoII(corrin)] subsystem may coexist with the formation of OO-CH3, followed by immediate relaxation of the subsystems in the ground state. Moreover, the formation of the OO-CH3 species followed by the formation of the {[CoIII(corrin)]-OO-CH3}+ complex stabilizes the system compared to the reactant complex.

Size-dependent catalytic hydrogen production via methane decomposition and aromatization at a low-temperature using Co, Ni, Cu, Mo, and Ru nanometals.

Catalysts of methane decomposition to hydrogen and aromatization are inevitable for the development of natural gas applications. Metal catalysts have been developed to achieve highly efficient methane decomposition and aromatization under 1000 K using various substrates, such as zeolites and silica. Here, we performed a consecutive study on methane decomposition using Co-, Ni-, Cu-, Mo-, and Ru-based nanocatalysts in the bulk, on a SiO2 substrate, and in mesoporous SiO2. The crystallite sizes of the bulk nanocatalysts, and nanocatalysts on nonporous and mesoporous SiO2 were controlled to 80-85, 30-70, and 3-11 nm, respectively. The nanocatalysts on mesoporous SiO2 exhibited high activity on hydrogen and benzene productions via methane decomposition, owing to the nanosize effect of the nanocatalysts and adsorption potentials in the SiO2 mesopores. In particular, the Ni nanocatalysts on mesoporous SiO2 exhibited hydrogen production activity from 650 K, which was the lowest temperature, compared with those in previous reports on hydrogen production. In addition, the catalytic activity was maintained for over 15 h at 650 and 800 K with recyclability. The overoxidation of Ni species in the SiO2 mesopores might have promoted the transformation reaction of CH4 to CHx and prevented coking by the largeness of the SiO2 mesopores in comparison with microporous media.

Plasma Promotes Dry Reforming Reaction of CH4 and CO2 at Room Temperature with Highly Dispersed NiO/γ-Al2O3 Catalyst

Plasma is an efficient method that can activate inert molecules such as methane and carbon dioxide in a mild environment to make them reactive. In this work, we have prepared an AE-NiO/γ-Al2O3 catalyst using an ammonia-evaporation method for plasma promoted dry reforming reaction of CO2 and CH4 at room temperature. According to the characterization data of XRD, H2-TPR, TEM, XPS, etc., the AE-NiO/γ-Al2O3 catalyst has higher dispersion, smaller particle size and stronger metal-support interaction than the catalyst prepared by the traditional impregnation method. In addition, the AE-NiO/γ-Al2O3 catalyst also exhibits higher activity in dry reforming reaction. This work provides a feasible reference experience for the research of plasma promoted dry reforming reaction catalysts at room temperature.

Low-Temperature Activation of Methane with Nitric Oxide and Formation of Hydrogen Cyanide over an Alumina-Supported Platinum Catalyst

This study demonstrated methane activation with subsequent conversion to hydrogen cyanide (HCN) at low temperatures using nitric oxide (NO) as the sole oxidant together with an alumina-supported platinum catalyst (Pt/Al2O3). This process afforded HCN even at 300 °C, indicating that C–H bond cleavage, NO dissociation, and simultaneous C–N coupling all occurred at this reduced reaction temperature. The HCN yield increased with increasing temperature, resulting in a 3.2% yield with a selectivity of 49% at 425 °C. This yield was much greater than that obtained from the reaction of CH4 with NH3 and O2, which suggests a reaction mechanism different from the Andrussow process. The HCN production rate was 11.4 mmol g–1 h–1 and the corresponding turnover frequency was 253 h–1, both of which were far superior to those obtained in previous studies at similar reaction temperatures. The Pt catalyst was found to be stable and could continuously produce HCN for at least 100 h. In situ X-ray absorption fine structure analyses suggested that the high resistance of this material to deep oxidation facilitated HCN formation. The difference between X-ray absorption near-edge structure spectra before and during the reaction indicated that the specific adsorbates on the catalyst were dependent on the reaction temperature and that the extent of adsorbed Pt-CN species was correlated with the reactivity of the material.

Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh

Abstract. Emissions of greenhouse gases (GHGs) from the Indian subcontinent have increased during the last 20 years along with rapid economic growth; however, there remains a paucity of GHG measurements for policy-relevant research. In northern India and Bangladesh, agricultural activities are considered to play an important role in GHG concentrations in the atmosphere. We performed weekly air sampling at Nainital (NTL) in northern India and Comilla (CLA) in Bangladesh from 2006 and 2012, respectively. Air samples were analyzed for dry-air gas mole fractions of CO2, CH4, CO, H2, N2O, and SF6 and carbon and oxygen isotopic ratios of CO2 (δ13C-CO2 and δ18O-CO2). Regional characteristics of these components over the Indo-Gangetic Plain are discussed compared to data from other Indian sites and Mauna Loa, Hawaii (MLO), which is representative of marine background air. We found that the CO2 mole fraction at CLA had two seasonal minima in February–March and September, corresponding to crop cultivation activities that depend on regional climatic conditions. Although NTL had only one clear minimum in September, the carbon isotopic signature suggested that photosynthetic CO2 absorption by crops cultivated in each season contributes differently to lower CO2 mole fractions at both sites. The CH4 mole fraction of NTL and CLA in August–October showed high values (i.e., sometimes over 4000 ppb at CLA), mainly due to the influence of CH4 emissions from the paddy fields. High CH4 mole fractions sustained over months at CLA were a characteristic feature on the Indo-Gangetic Plain, which were affected by both the local emission and air mass transport. The CO mole fractions at NTL were also high and showed peaks in May and October, while CLA had much higher peaks in October–March due to the influence of human activities such as emissions from biomass burning and brick production. The N2O mole fractions at NTL and CLA increased in June–August and November–February, which coincided with the application of nitrogen fertilizer and the burning of biomass such as the harvest residues and dung for domestic cooking. Based on H2 seasonal variation at both sites, it appeared that the emissions in this region were related to biomass burning in addition to production from the reaction of OH and CH4. The SF6 mole fraction was similar to that at MLO, suggesting that there were few anthropogenic SF6 emission sources in the district. The variability of the CO2 growth rate at NTL was different from the variability in the CO2 growth rate at MLO, which is more closely linked to the El Niño–Southern Oscillation (ENSO). In addition, the growth rates of the CH4 and SF6 mole fractions at NTL showed an anticorrelation with those at MLO, indicating that the frequency of southerly air masses strongly influenced these mole fractions. These findings showed that rather large regional climatic conditions considerably controlled interannual variations in GHGs, δ13C-CO2, and δ18O-CO2 through changes in precipitation and air mass.

Effect of Pd doping in (Fe/Ni)/CeO2 catalyst for the reaction path in CO2 oxidative ethane dehydrogenation/reforming

The catalytic reaction of C2H6 with CO2 provides an opportunity to use shale gas and the greenhouse gas as source materials to produce ethylene through oxidative dehydrogenation or produce syngas through dry reforming. In this work, the reaction characteristics of ethane with CO2 on Fe/Co/Ni/Cu monometallic catalysts and Pd-doped bimetallic catalysts were studied through activity test, kinetic analysis, catalyst characterization and DFT calculation. It is found that Pd–Fe6/CeO2 has a high and stable C2H4 selectivity of 80.4%, which is suitable for oxidative dehydrogenation reaction, while Ni6/CeO2 has a large ethane/CO2 conversion and a high CO selectivity of 96.5%, which is suitable for dry reforming reaction. For Fe-based catalyst, the doping of Pd form double active component structure. It only reduces the energy barrier of ethylene formation and CO2 direct activation to provide O∗, but also increases the energy barrier of ethylene deep dehydrogenation, thus increasing the conversion of reactants and selectivity of C2H4. For Ni-based catalysts, the doping of Pd forms the alloy structure, which reduces the energy barrier of O∗-assisted dehydrogenation reaction and increases the conversion of reactants, but increases the energy barrier of C–C bond cleavage and CO2 activation reaction, which reduces the selectivity of reforming to syngas.

Analytical study of CO2–CH4 exchange in hydrate at high rates of carbon dioxide injection into a reservoir saturated with methane hydrate and gaseous methane

An injection of carbon dioxide into depleted methane deposits has a dual-purpose: to stimulate the production of the residual natural gas and to store carbon dioxide. Of a great interest is the special case when a methane deposit contains methane hydrate. When carbon dioxide is injected under suitable thermodynamic conditions, the methane hydrate is converted to carbon dioxide hydrate. The mechanism of conversion during the injection of gaseous carbon dioxide into a reservoir, saturated with methane hydrate and methane is investigated. This mechanism is based on the difference between the heat required to dissociate methane hydrate and the heat released during the formation of carbon dioxide hydrate. As a result, a self-sustained replacement reaction may develop. In this work a new mathematical model which describes the replacement reaction of CH4 by CO2 in hydrate at a high injection rate is developed. A moving interface on which carbon dioxide replaces methane in hydrate is introduced and full system of boundary conditions is derived. Using an analytical similarity solution, various reaction regimes are explored. The obtained critical diagrams give the range of the main parameters at which the conversion of CH4 hydrate to CO2 hydrate is realized.

Improved Constraints on Global Methane Emissions and Sinks Using δ 13C-CH4.

We study the drivers behind the global atmospheric methane (CH4) increase observed after 2006. Candidate emission and sink scenarios are constructed based on proposed hypotheses in the literature. These scenarios are simulated in the TM5 tracer transport model for 1984–2016 to produce three‐dimensional fields of CH4 and δ 13C‐CH4, which are compared with observations to test the competing hypotheses in the literature in one common model framework. We find that the fossil fuel (FF) CH4 emission trend from the Emissions Database for Global Atmospheric Research 4.3.2 inventory does not agree with observed δ 13C‐CH4. Increased FF CH4 emissions are unlikely to be the dominant driver for the post‐2006 global CH4 increase despite the possibility for a small FF emission increase. We also find that a significant decrease in the abundance of hydroxyl radicals (OH) cannot explain the post‐2006 global CH4 increase since it does not track the observed decrease in global mean δ 13C‐CH4. Different CH4 sinks have different fractionation factors for δ 13C‐CH4, thus we can investigate the uncertainty introduced by the reaction of CH4 with tropospheric chlorine (Cl), a CH4 sink whose abundance, spatial distribution, and temporal changes remain uncertain. Our results show that including or excluding tropospheric Cl as a 13 Tg/year CH4 sink in our model changes the magnitude of estimated fossil emissions by ∼20%. We also found that by using different wetland emissions based on a static versus a dynamic wetland area map, the partitioning between FF and microbial sources differs by 20 Tg/year, ∼12% of estimated fossil emissions.

A comprehensive kinetic modeling study of ethylene combustion with data uncertainty analysis

A revision and upgrade of the ethylene (C2H4) oxidation kinetic sub-mechanism were carried as a next step in the optimization of the C<3 chemistry, which is a base for the upcoming PAH sub-model improvement. The main emphasis of the work was focused on the assessment of uncertainties of the thermo-kinetical and experimental data to involve that principally in the methodology of reaction model uncertainty. The principal targets of mechanism extension and update are: inspection of the reaction rate coefficients with accounting recently published pressure-dependent reactions and analysis of reaction paths related to the C2H4 low-temperature oxidation and the formation of aromatic precursors. The experimental data (auto-ignition, premixed laminar flame speeds, and concentration profiles) with evaluated uncertainty and consistency were used for model optimization. The uncertainty bounds of the key reaction rate coefficients were evaluated from the statistical treatment of the published data, which provided constraints in the reaction rate parameters. The rate parameters of 57 reactions of C2H4 and key intermediates were optimized. The revised reaction mechanism demonstrates a good agreement with the majority of the existing experimental data. Results of the sensitivity and rate of production analyses performed for several kinetic mechanisms from the literature were compared to visualize the variations and ambiguity in the importance of reaction paths and highlight the uncertainty problems in mechanism optimization and integration.

Revisit laminar premixed ethylene flames at elevated pressures: A mass spectrometric and laminar flame propagation study

This work reports investigations on laminar premixed ethylene (C2H4) flames with special interests on measurements and kinetic modeling at elevated pressures. Chemical structures of laminar premixed C2H4/O2/Ar flames at 3 and 5 atm with the equivalence ratio of 1.4 were measured with molecular beam mass spectrometry. Both the stable and reactive species were identified and quantified in this work. Among them, the mole fractions of H and OH are evidently dependent on pressures. Laminar flame propagation of C2H4/air mixtures at 1 and 2 atm and that of C2H4/O2/He mixtures at 2 and 5 atm were also investigated in a high pressure constant-volume cylindrical combustion vessel at an unburnt temperature (Tu) of 298 K and equivalence ratios of 0.7–1.5. Besides, a kinetic model for C2H4 combustion was developed based on the evaluations of critical reactions with special concerns on recent theoretical calculation progress and validated against both the new data in this work and previous data of ethylene combustion in literature. The updated reactions of C2H4 + O from recent theoretical calculations in the present model can improve the predictions of both the flame speciation results and the laminar burning velocities (LBVs) under rich and elevated pressure conditions. Compared with previous models, C2H4 + O = 3CH2 + CH2O instead of C2H4 + O = CH3 + HCO becomes a major consumption pathway of C2H4 in the present model. This results in the lower production of CH3 which is responsible for the chain termination under rich and elevated pressure conditions. Therefore, the present model could lower down the predictions of the CH3-related speciation data and improve the LBV predictions under rich and elevated pressure conditions.

Insight into Acetic Acid Synthesis from the Reaction of CH4and CO2

The reaction of CH4 and CO2 to produce acetic acid is an atom-efficient way for using carbon resources and for mitigating CO2 emissions. This article provides a critical assessment of the progress ...

Methane chemistry in a nutshell – the new submodels CH4 (v1.0) and TRSYNC (v1.0) in MESSy (v2.54.0)

Abstract. Climate projections including chemical feedbacks rely on state-of-the-art chemistry–climate models (CCMs). Of particular importance is the role of methane (CH4) for the budget of stratospheric water vapour (SWV), which has an important climate impact. However, simulations with CCMs are, due to the large number of involved chemical species, computationally demanding, which limits the simulation of sensitivity studies. To allow for sensitivity studies and ensemble simulations with a reduced demand for computational resources, we introduce a simplified approach to simulate the core of methane chemistry in form of the new Modular Earth Submodel System (MESSy) submodel CH4. It involves an atmospheric chemistry mechanism reduced to the sink reactions of CH4 with predefined fields of the hydroxyl radical (OH), excited oxygen (O(1D)), and chlorine (Cl), as well as photolysis and the reaction products limited to water vapour (H2O). This chemical production of H2O is optionally fed back onto the specific humidity (q) of the connected general circulation model (GCM), to account for the impact onto SWV and its effect on radiation and stratospheric dynamics. The submodel CH4 is further capable of simulating the four most prevalent CH4 isotopologues for carbon and hydrogen (CH4 and CH3D, as well as 12CH4 and 13CH4). Furthermore, the production of deuterated water vapour (HDO) is, similar to the production of H2O in the CH4 oxidation, optionally passed back to the isotopological hydrological cycle simulated by the submodel H2OISO, using the newly developed auxiliary submodel TRSYNC. Moreover, the simulation of a user-defined number of diagnostic CH4 age and emission classes is possible, the output of which can be used for offline inverse optimization techniques. The presented approach combines the most important chemical hydrological feedback including the isotopic signatures with the advantages concerning the computational simplicity of a GCM, in comparison to a full-featured CCM.

Theoretical analysis of the mechanisms of reactions of unsaturated C&lt;sub&gt;4&lt;/sub&gt;H&lt;sub&gt;6 &lt;/sub&gt;hydrocarbons with a highly reactive CH radical

Theoretical analysis of the mechanisms of reactions of unsaturated C&lt;sub&gt;4&lt;/sub&gt;H&lt;sub&gt;6 &lt;/sub&gt;hydrocarbons with a highly reactive CH radical

Numerical Investigations on Methane–Air Nanosecond Pulsed Dielectric Barrier Discharge Plasma-Assisted Combustion

Plasma-assisted combustion is a promising approach to achieve fast ignition and highly efficient combustion. In this work, methane–air nanosecond pulsed dielectric barrier discharge plasma-assisted combustion is numerically investigated by combining a homemade plasma model with the combustion model of software CHEMKIN-PRO. Effects of varying applied voltage amplitudes on the characteristic parameters of the plasma-assisted planar shear flow combustion as well as the reaction pathway maps of not only the nanosecond pulsed dielectric barrier discharge plasma but also the combustions without and with plasma assistance are systematically illustrated and analyzed. The simulation results indicate that under the combined action of increasing electric field intensity and increasing charged particle densities, the peak value of the discharge current density increases, and the peak time of the discharge current density is brought forward with the increase of the applied voltage amplitude. The temperature reaches its peak value earlier in the methane–air combustion with plasma assistance than without plasma assistance. The maximum temperature reduces to around 1900 K when the applied voltage amplitude is higher than 11 kV. There are emerging pathways to generate hydrocarbons C2H4 and C2H2 in the plasma-assisted combustion, the reactions of CH4 on CH and C2H on H2, respectively. The reactions involving active species such as H play a significant role in the plasma-assisted combustion, which causes an obvious decrease in the densities of these active species with plasma assistance.

Prediction of the product channels in the reaction of the methyl radical with fulminic acid

AbstractThe reaction of CH3 + HCNO was theoretically studied by both density functional theory and molecular orbital calculations and analyzed by quantum statistical methods. The potential energy surface was constructed at the UCCSD(T)//B3LYP/6‐311++G(3df,2p) + ZPE level. Four entrance channels are opened relating to the interaction of the CH3 radical with each of the four atoms of the HCNO molecule, giving rise to 18 different product sets. The predicted geometries and heats of reaction are in good agreement with available experimental data. The major pathways involve addition of CH3 to the C atom of HCNO with a small energy barrier of ∼4 kcal/mol forming both Z and E‐HC(CH3)NO (IS1/IS1b) intermediates lying 45 or 44 kcal/mol, respectively, below the reactants. The nascent intermediates can collisionally be deactivated and subsequently decomposed into H + CH3CNO or isomerized prior to decomposition giving other products. Kinetics calculations covering the temperature range of 400‐2500 K, under pressures of 7.6 × 10–1 to 7.6 × 105 Torr for N2, He, and Ar as the third bodies show that at 760 Torr N2, the adducts including both IS1 and IS1b are the major products at temperature below 600 K, whereas H + CH3CNO and CNO + CH4 are the major products at T ≥ 1500 K. The total high‐pressure rate coefficient can well be expressed by the following three‐parameter equation: k(T) = 7.75 × 10–16 T1.69 exp (−1480 K/T) cm3 molecule–1 s–1.

Kinetic analysis of diffusion combustion of low calorific value gas under the action of thermal dynamics

At present, a large number of low calorific value gases are directly discharged, which will not only pollute the environment, but also wastes resources. In view of the difficulty in burning low calorific value gas, based on the numerical simulation software Fluent, this paper studies the reaction kinetics of diffusive combustion of low calorific value gas under the action of thermal dynamics, and analyzes the distribution of the gas concentration field in the furnace, the reaction turbulent rate and the reaction equivalent ratio change of the combustion reaction of CH4, CO, H2 in the blast furnace gas as well. The results show that the air preheating temperature increases, the O2 concentration decreased and the CO concentration increases. On the same cross section, as the air preheating temperature increases, the reaction turbulence of CH4 decreases. When Ta = 350 K, the turbulent rate of the combustion reaction of CO and H2 reaction in the complete combustion stage is the largest, turbulent rates are 6.68698E-5 and 2.8484E-7, respectively. With the increase of air preheating temperature, the higher the reaction equivalent ratio of the combustion reaction of CH4, CO and H2. When Ta = 450 K, the change trend of the reaction equivalent ratio of the three combustion reactions of CH4, CO and H2 is the same, the minimum peak values are 1.42458, 3.22563 and 0.72694, respectively, and the reaction equivalent ratio of CO is the highest. At this temperature, the complete combustion of the CO component in the low calorific value gas can be promoted.

C/C Exchange in Activation/Coupling Reaction of Acetylene and Methane Mediated by Os+: A Comparison with Ir+, Pt+, and Au.

The activation and coupling reactions of methane and acetylene mediated by M+ (M = Os, Ir, Pt, and Au) have been comparatively studied at room temperature by the techniques of mass spectrometry in conjunction with theoretical calculations. Studies have shown that Os+ and Ir+ can mediate the activation/coupling reaction of CH4 and C2H2, while Pt+ and Au+ cannot, which could be explained by the number of empty valence orbitals in the metal atom. In addition, there are different competition channels for the reaction mediated by Os+ and Ir+: an expected dehydrogenation and an unexpected C/C exchange. We find that if the rare C/C exchange reaction takes place, there are symmetric carbon atoms in the reaction intermediate and the C/C exchange reaction is favored kinetically. The C/C exchange reaction must be considered, which will affect the yield of the products in the primary reaction. This study shows the molecular-level mechanisms which include the C/C exchange reaction in the activation and coupling reaction of organic compounds mediated by different metals.