Single-step Mechanism Research Articles

Syn-Propanethial S-Oxide as an Available Natural Building Block for the Preparation of Nitro-Functionalized, Sulfur-Containing Five-Membered Heterocycles: An MEDT Study.

The regio- and stereoselectivity and the molecular mechanisms of the [3 + 2] cycloaddition reactions between Syn-propanethial S-oxide and selected conjugated nitroalkenes were explored theoretically in the framework of the Molecular Electron Density Theory. It was found that cycloadditions with the participation of nitroethene as well as its methyl- and chloro-substituted analogs can be realized via a single-step mechanism. On the other hand, [3 + 2] cycloaddition reactions between Syn-propanethial S-oxide and 1,1-dinitroethene can proceed according to a stepwise mechanism with a zwitterionic intermediate. Finally, we evaluated the affinity of model reaction products for several target proteins: cytochrome P450 14α-sterol demethylase CYP51 (RSCB Database PDB ID: 1EA1), metalloproteinase gelatinase B (MMP-9; PDB ID: 4XCT), and the inhibitors of cyclooxygenase COX-1 (PDB:3KK6) and COX-2 (PDB:5KIR).

Transglutaminase–mucin binding dynamics in gastrointestinal mucus: Interfacial behaviour, thermodynamics and gelation mechanism

Transglutaminase, an enzyme present in epithelial cells and as a residual component in processed foods, is hypothesised to interact with gastrointestinal mucus, impacting its structure and function. To test the physical validity of this phenomenon, this study investigates the binding kinetics and thermodynamics between porcine gastric mucin (PGM) and microbial transglumatinse (TGM) in a model gastrointestinal mucus, followed by the rheological analysis of the resulting systems. At pH 7, TGM exhibited pronounced binding with the PGM interface, characterised by a high surface density (55.34 ± 1.86 µg/m−2) and a low dissociation constant (KD ∼ 4.03 ± 0.10 μM) as determined by surface plasma resonance (SPR). Conversely, at pH 3, TGM showed weak adhesion onto PGM, resulting in a less stable binding, reflected by a lower surface density (10.94 ± 0.67 µg/m−2) and a higher dissociation constant (KD ∼ 6.24 ± 0.22 μM). Regardless of the nature of interaction, the Hill coefficients (nH ≥ 1) indicated that the binding sites were markedly denser at pH 7 (1383.38 ± 46.47 pmol/m−2), than at pH 3 (273.68 ± 16.84 pmol/m−2). Fluorimetry analysis suggested temperature-dependent dynamic binding between PGM and TGM. The resulting Benesi – Hildebrand plots illustrated a linear correlation between PGM and increasing TGM concentration, suggesting a single-step interaction mechanism. The calculated thermodynamic parameters indicated spontaneous interaction between PGM and TGM (ΔG < 0) via endothermic (entropic) interactions (ΔH > 0). Notably, hydrophobic forces played a significant role in the network stabilisation of PGM−TGM complex (ΔS > 0). Rheometry analysis elucidates that the interaction maxima within TGM−PGM systems substantially elevate both shear viscosity (η), and the melting point (Tm), shifting from 6.75 ± 0.28 to 70.94 ± 2.21 (×10−3) Pa s (at 1 s−1), and 36.80 ± 0.80 to 48.20 ± 0.11 °C, respectively. Furthermore, the coexistence of these two macromolecular species results in a 3- to 4-fold dramatic increase in the viscoelastic moduli of the binary complex. These findings build a strong physicochemical basis for the interaction between TGM and PGM, with profound effects on the rhological behaviour of the latter; it also highlights the need to examine the biochemical/enzymatic aspects of said interactions, and their potential effects on mucosa and human physiology.

ADME Study, Molecular Docking, Elucidating the Selectivities and the Mechanism of [4 + 2] Cycloaddition Reaction Between (E)-N ((dimethylamino)methylene)benzothioamide and (S)-3-acryloyl-4-phenyloxazolidin-2-one.

The molecular electron density theory (MEDT) was employed to examine the [4 + 2] cycloaddition reaction between (E)-N-((dimethylamino)methylene)benzothioamide (1) and (S)-3-acryloyl-4-phenyloxazolidin-2-one (2) at the B3LYP/6-311++G(d,p) design level. Parr functions and energy studies clearly show that this reaction is regio- and stereoselective, in perfect agreement with experimental results. By evaluating the chemical mechanism in terms of bond evolution theory (BET) and electron localization function (ELF), which divulges a variety of variations in the electron density along the reaction path, a single-step mechanism with highly asynchronous transition states structures was revealed. Additionally, we conducted a docking study on compounds P1, P2, P3, and P4 in the SARS-CoV-2 main protease (6LU7) in comparison to Nirmatrelvir. Our findings provide confirmation that product P4 may serve as a potent antiviral drug.

On the Question of Zwitterionic Intermediates in the [3+2] Cycloaddition Reactions between Aryl Azides and Ethyl Propiolate.

The molecular mechanism of the [3+2] cycloaddition reactions between aryl azides and ethyl propiolate was evaluated in the framework of the Molecular Electron Density Theory. It was found that independently of the nature of the substituent within the azide molecule, the cycloaddition process is realized via a polar but single-step mechanism. All attempts of localization as postulated earlier by Abu-Orabi and coworkers' zwitterionic intermediates were not successful. At the same time, the formation of zwitterions with an "extended" conformation is possible on parallel reaction paths. The ELF analysis shows that the studied cycloaddition reaction leading to the 1,4-triazole proceeds by a two-stage one-step mechanism. It also revealed that both zwitterions are created by the donation of the nitrogen atom's nonbonding electron densities to carbon atoms of ethyl propiolate.

Estimation and testing of single-step oxidation reactions for hydrogen and methane in low-oxygen, elevated pressure conditions

Advanced combustion concepts, such as moderate or intense low-oxygen dilution (MILD) combustion, offer a reduction in NOx emissions and increased thermal efficiency. MILD is characterised by low-oxygen, high-temperature conditions, where finite-rate chemistry effects are significant. Modelling this regime using reduced or single-step chemistry remains a challenge in part due to the finite-rate chemistry. This work proposes a generalised method for assigning Arrhenius coefficients of a single-step reaction using the outputs of a detailed mechanism. Assigning the typical chemical conservation equation to a progress variable, activation energy and pre-exponential factor for an Arrhenius kinetics global reaction are determined for hydrogen and methane across a number of conditions, with the proposed method extended to n-heptane as well. The temperature exponent in the modified Arrhenius equation is determined by minimising the ignition delay error between detailed and single-step simulations. Functional forms of each coefficient are calculated from a multivariate regression, dependent on initial temperature, pressure, and oxidant mole fraction. The predicted mechanisms are compared against the detailed kinetics in closed homogeneous batch reactors, with comparisons for hydrogen extended to both laminar opposed flow diffusion flames, and computational fluid dynamics (CFD) simulations. Ignition delay and equilibrium temperature are both well predicted for all three fuels in the batch reactors. Notably, the negative temperature coefficient behaviour of n-heptane is successfully recreated with the single-step mechanism. Temperature and heat release of hydrogen flames are well captured in both opposed flow laminar flames, and in turbulent CFD simulations. The computational time was also significantly reduced through the single-step mechanisms, resulting in ∼100 times reduction in compute time for CFD simulations. The function form of the Arrhenius coefficients shows promise for extension outside of the ranges and fuels analysed herein, and presents interesting phenomena for exploring how initial reactant temperature and pressure influence the effective activation energy of an oxidation process.

Fully Selective Synthesis of Spirocyclic-1,2-oxazine N-Oxides via Non-Catalysed Hetero Diels-Alder Reactions with the Participation of Cyanofunctionalysed Conjugated Nitroalkenes.

Hetero Diels-Alder (HDA) reactions with the participation of E-2-aryl-1-cyano-1-nitroethenes and methylenecyclopentane were evaluated on the basis of experimental as well as quantumchemical data. It was found that contrary to most known HDA reactions, title processes are realised under non-catalytic conditions and with full regiocontrol. The DFT study shows, without any doubt, the polar but single-step reaction mechanism. Deeper exploration using Bonding Evolution Theory (BET) techniques gives a clear image of the sequences of electron density reorganisation along the reaction coordinate. The first C4-C5 bond is created in phase VII by merging two monosynaptic basins, while the second O1-C6 bond is created in the last phase by a donation of the nonbonding electron density of O1 to C6. Based on the research, we can conclude that the analysed reaction proceeds according to a two-stage one-step mechanism.

The importance of nuclear dynamics in reaction mechanisms of acetylene cyclotrimerization catalyzed by Fe+-compounds

The reaction mechanism of transition metal-catalyzed [2 + 2 + 2] cyclotrimerization of three acetylenes to form benzene consists of multiple steps, including the generation of a metallacyclopentadiene intermediate through the coupling of two acetylenes and subsequent [4 + 2] cycloaddition. Using quantum chemical calculations, we show that acetylene cyclotrimerization catalyzed by Fe+–L-type compounds (where L represents the ligands F−, Cl−, OH−, SH−, NC−, NH3, H2O, and cyclopentadienyl anion) can occur via a concerted single-step mechanism, where the reactant complex (C2H2)3–Fe+–L is directly connected to the C6H6–Fe+–L product complex via a single intrinsic reaction coordinate (IRC) path with one transition state. We then performed trajectory calculations, starting from concerted transition state structures with small kinetic energies, to confirm the efficient formation of benzene via this single-step mechanism. Interestingly, we found that many of the trajectories exhibited non-IRC dynamics—the trajectories did not directly lead to the formation of the benzene product, but to that of the C2H2–Fe+–L–C4H4 intermediate; in contrast, direct benzene formation predominantly occurred for the compounds comprising the ligands F− and NC−. Thus, we report that nuclear dynamics play an important role in determining the cyclotrimerization reaction mechanism, and that the properties of the potential energy surface depend on the ligand molecule.

Understanding the Regioselectivity and the Molecular Mechanism of [3 + 2] Cycloaddition Reactions between Nitrous Oxide and Conjugated Nitroalkenes: A DFT Computational Study

Regiochemical aspects and the molecular mechanism of the [3 + 2] cycloaddition between nitrous oxide and conjugated nitroalkenes were evaluated on the basis of the wb97xd/6-311 + G(d) (PCM) computational study. It was found that, independently of the nature of the nitroalkene, all considered processes are realized via polar, single-step mechanisms. All attempts at the localization of hypothetical zwitterionic intermediates were unsuccessful. Additionally, the DFT computational study suggested that, in the course of the reaction, the formation of respective Δ2-4-nitro-4-R1-5-R2-1-oxa-2,3-diazolines was preferred from the kinetic point of view.

A new method for systematic 1-step chemistry reduction applied to hydrocarbon combustion

We propose a new single-step mechanism for the combustion of arbitrary hydrocarbons and alcohols. Unlike most single-step models, no tabulation is required, as the method builds upon a new analytical description of the thermochemical equilibrium of fuel-oxidizer mixtures including dihydrogen and carbon monoxide – two species usually discarded in one-step descriptions – yielding correct adiabatic temperature. The single-step chemistry includes varying stoichiometric coefficients, ensuring a convergence towards thermochemical equilibrium regardless of the local state. The reaction rate is then carefully adjusted to reproduce accurately premixed flames. To tackle ignition simultaneously, an additional passive scalar advection-diffusion-reaction equation is introduced, with a rate fitted on ignition delays. The scalar then serves as an efficiency to modify the single-step reaction rate in autoignition configurations. The obtained scheme is then validated for a wide range of equivalence ratios on homogeneous reactors, premixed flames, a triple flame, and a counterflow diffusion flame. The new analytical thermochemical equilibrium formulation may also serve in speeding up infinitely fast chemistry calculations.

Comparative assessment of the biomass solar pyrolysis biochars combustion behavior and zinc Zn(II) adsorption

Biochars from solar pyrolysis of the waste straw, and dried sewage sludge, were assessed to recognize the possible application as unconventional adsorbents and fossils replacements for combustion purposes. The adsorption properties of the biochars were characterized by the BET (Brunauer, Emmett, and Teller) surface area, pore volumes, and the degree of Zn(II) adsorption from aqueous solutions. A higher removal degree of zinc ions of 26% was noted for biochars from dried sewage sludge with a BET area of 40.84 m2/g, compared to the waste straw biochars with a BET area of 1.67 m2/g and a corresponding removal degree of 16%. Both biochars presented more uniform combustion behavior compared to raw biomass, with the ignition and burnout temperatures similar to coal. Solar pyrolysis caused a reduction of the combustion kinetic steps, from multi-step combustion of the raw biomass to a single-step and two-step kinetic mechanisms for the sewage sludge and waste straw biochars respectively. It was found that the waste straw biochars are possible alternative fuels with a higher heating value of 22.6 MJ/kg, while sewage sludge chars presented better zinc adsorption of 2.09 mg/g and a total removal degree of 26%.

Single-Step Mechanism for Regioselective Nitration of 9,10-BN-Napthalene with Acetyl Nitrate in the Gas Phase.

The energetics of the regioselective mononitration of 9,10-BN-naphthalene with acetyl nitrate (H3C2NO4) were modeled with ab initio simulations in the gas phase and an acetonitrile solvent. The single-electron-transfer (SET) nitration mechanism leading to a σ-complex and a single-step nitration mechanism were modeled. The energy barrier for the single-step mechanism was lower than that for the SET mechanism in the gas phase. However, the two are much more energetically competitive in the solvent. The σ-complex was found to be unstable in the gas phase owing to the interaction with the counterion. Using the single-step mechanism, the carbon site 1 nearest boron had the lowest activation energy for nitration of 22.6 kcal/mol, while site 3 had the second lowest barrier of 24.6 kcal/mol. Details on the molecular structures at intermediate and transition states as well as charges in different configurations are discussed.

Kinetics of ATP/ADP binding to the gp16 ATPase

The gp16 ATPase is the constituent subunit of the pentameric dsDNA (double-stranded deoxyribonucleic acid) translocation motor of the Bacillus subtilis Φ29 bacteriophage. Although recent single-molecule studies have provided tantalizing clues about the activity of this motor, the mechanism by which the gp16 subunits couple the energy obtained from the binding and hydrolysis of ATP to the mechanical work of dsDNA translocation remains unknown. To address this need, we have characterized the binding of fluorophore-labeled ATP and ADP to monomeric gp16 using a stopped-flow fluorescence assay. These experiments show that the binding of ATP/ADP occurs through a single-step mechanism with corresponding affinities of 523.8 ± 247.3 nM for ATP and a lower limit of 30 μM for ADP. When analyzed through the lens of changes in free energy of the system, this difference in binding affinities is reasonable for a cyclical process of binding, hydrolysis, and product release. In addition to answering questions about the activity of monomeric gp16, these results are also a necessary step in constructing a model for intersubunit communication within the pentameric gp16 motor.

Mapping of β-lactoglobulin − mucin interactions in an in vitro astringency model: Phase compatibility, adsorption mechanism and thermodynamic analysis

This study investigates the astringency-related interfacial behaviour, mechanistic parameters, and interaction mechanisms of a typical milk protein, β-lactoglobulin (β-LG), with mucin acting as model salivary protein. For a series of β-LG – mucin compositions, the most intense phase separation is observed for a 75:25 w/w mixture of mucin and β-LG at pH 3. QCM-D shows that, at pH 3, β-LG adsorption on a mucinous interface yields a heavily-hydrated viscoelastic layer with increased energy dissipation [ΔD ≤ 9.92 ± 0.01 ( × 10−6], thickness (Δt = 25.51 ± 0.01 nm), and wet mass values (Δm = 2623.30 ± 1.27 ng cm−2). At pH 7, β-LG (Δm = 855.86 ± 0.45 ng cm−2) forms highly-ordered (more rigid), relatively less dissipative, but thinner interfacial layer, as indicated by the decreased Δt (7.13 ± 0.01 nm) and ΔD values [≤ 2.52 ± 0.01 ( × 10−6)]. Furthermore, ΔD vs.Δf plots point to the existence of greater conformational and molecular reordering upon progressive coupling of β-LG at pH 3, as compared to pH 7. β-LG exhibits a two-step binding with mucin at pH 3; whilst a single-step (low affinity) mechanism exists at pH 7, as elucidated by fluorimetry. Thermodynamic analysis suggests two macromolecular populations interact spontaneously (ΔG < 0) regardless of pH. Interestingly, ΔS values are substantially greater at pH 3 (≥182.76–292.30 J K−1M−1), in comparison with pH 7 (≤17.07 J K−1M−1); suggesting that entropy-driven flocculation of β-LG and mucin arise from well-defined electrostatic and/or hydrophobic forces. The above results highlight the inherent complexity of pH-induced β-LG – mucin interactions, and the resulting complexity of the physicochemical basis of astringency.

Pre-Crystallization Criteria and Triple Crystallization Kinetic Parameters of Amorphous–Crystalline Phase Transition of As40S45Se15 Alloy

This framework focuses mainly on a detailed study of the pre-crystallization criteria that characterize the As40S45Se15 glassy alloy in various heating rates ranging from 5 to 40 (K/min) by Differential Scanning Calorimetry (DSC). These criteria aim to clarify the relationship of the tendency of glass-forming by the heating rate for the investigated glassy alloy. The crystallization parameters were calculated using different methods.The activation energy of crystallization Ec(χ) as a function of conversion (χ) was obtained using the iso-conversional models of Flynn–Wall–Ozawa (FWO), Starink and Kissinger–Akahira–Sunose (KAS). The results show a slight increase of Ec(χ) with conversion (χ) which accounts for a single-step mechanism controlling the crystallization process. Moreever, the conversion dependence of the Avrami exponent n(χ) show an increase with conversion (χ), average values of n(χ) can be accounted for two and three-dimensional crystal growth with heterogeneous nucleation. On the other hand, the fitting of the experimental DSC data to the calculated DSC curves indicated that the crystallization process of the studied glasses cannot be satisfactorily described by the Johnson–Mehl–Avrami (JMA) model. On the contrary (SB) model is more suitable to describe the crystallization process for the studied of As40S45Se15 Alloy. Finally, the crystalline structure of the study sample was recognized by X-ray diffraction (XRD) and electron scanning microscope (SEM).

Computational Study on Pazopanib and Pemetrexed Anticancer Drug Molecules Interacting with a Small Peptide Link

Cancer is a group of diseases that are defined as uncontrolled cell proliferation, impaired function of vital tissues and cell death. Chemotherapy is treatment using anti-cancer drugs to destroy cancer cells or control the growth of these cells. In chemotherapy applications pharmacologically active anticancer drugs reach with low specificity to tumor tissue, and also their toxicity is dose-dependent. Classical drug administration routes are either oral or intravenous. Orally taken pills result in irregular pharmacokinetics due to the passages of different metabolic pathways and their low specificity. This leads to frequent damage to healthy tissues. Nanoparticle containing drug delivery systems may overcome these harmful side effects partially (or sometimes totally). Binding peptide-drug conjugates inside of some appropriate nanoparticles is one of the prominent methods among targeted drug delivery systems. Such a system containing Pazopanib (Pz) and Pemetrexed (Pm) drug complexes attached to magnetite nanoparticles with a short polypeptide chain (Ala-Lys-Ala-Leu-Arg-Cys) were designed in our laboratory. In the present study, we computationally investigate the conjugation mechanisms of Pz and Pm drug molecules to the above-mentioned polypeptide chain. The stable structures on the complex formation pathways and their free energy values were obtained at the B3LYP/6-31G(d) level in the water. The mechanism of Pept-Pz complex formation has two steps whose free energy barriers are found to be 21.37 and 27.72 kcal/mol. On the other hand, the free energy barrier of the Pept-Pm complex having a single-step mechanism was calculated as 28.16 kcal/mol.

Experimental and Theoretical Mechanistic Study on the Thermal Decomposition of 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline.

The present paper is a continuation of comprehensive study regarding to synthesis and properties of pyrazoles and their derivatives. In its framework an experimental and theoretical studies of thermal decomposition of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline were performed. It was found, that the decompositions of the mentioned pyrazoline system in the solution and at the melted state proceed via completely different molecular mechanisms. These mechanisms have been explained in the framework of the Molecular Electron Density Theory (MEDT) with the computational level of B3LYP/6-31G(d). A Bonding Evolution Theory (BET) examination of dehydrochlorination of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline permits elucidation of the molecular mechanism. It was found, that on the contrary for most known HCl extrusion processes in solution, this reaction is realised via single-step mechanism.

1,3-Dipolar Cycloadditions by a Unified Perspective Based on Conceptual and Thermodynamics Models of Chemical Reactivity.

The main aim in the present report is to gain a deeper understanding of typical 1,3-dipolar cycloadditions by means of three chemical reactivity models in a unified perspective: conceptual density functional theory, distortion/interaction, and reaction force analysis. The focus is to explore the information provided by each reactivity model and how they complement or reinforce each other. Our results showed that the Bell-Evans-Polanyi (BEP) relationship is fulfilled, which is consistent with the Hammond-Leffler postulate. The electronic chemical potential based analysis classifies the reactions as HOMO-, HOMO/LUMO-, and LUMO-controlled reactions as the activation energy increases. It seems likely that HOMO-controlled reaction shifts into LUMO-controlled one as the transition state (TS) position does from early into late. Therefore, the transition from HOMO- (and early TS) into LUMO-controlled (and late TS) is paid by shifting the overall energy change into an endothermic direction, thus supporting the fulfillment of the BEP principle. While thermodynamic models unveil that the distortion or structural rearrangements mainly drive the activation barriers rather than interaction or electronic rearrangements in accord with the distortion/interaction and reaction force analysis, respectively. It is also found that both models are consistent when energy associated with structural and electronic reordering from reaction force analysis is respectively confronted with destabilizing (distortion and Pauli repulsion) and stabilizing (electrostatic and orbital interactions) contributions from the distortion/interaction model, which, on the other hand, increases as low activation barrier and high exothermicity are converted into the high barrier and low exothermicity along with the BEP relation. Finally, the reaction force constant reveals that all 1,3-dipolar cycloaddition reactions proceed by a synchronous single-step mechanism, unveiling that the degree of synchronicity is quite the same in all reactions, confirming the statement that BEP is fulfilled for similar reactions proceeding by a quite alike degree of synchronicity.

Numerical analysis of pulverized biomass combustion

Combustion of pulverized biomass in a laboratory swirl burner is computationally investigated. The two-phase flow is modelled by an Eulerian-Lagrangian approach. The particle size distribution and turbulent particle dispersion are considered. The radiative heat transfer is modelled by the P1 method. For modelling turbulence, different RANS modelling approaches are applied. The pyrolysis of the solid fuel is modelled by a single step mechanism. For the combustion of the volatiles a two-step reaction mechanism is applied. The gas-phase conversion rate is modelled by the Eddy Dissipation Model, combined with kinetics control. The results are compared with measurements.

Structure, microstructure and electrodeposition behaviours of aluminium from AlCl3-EMIC and AlCl3-BMIC ionic liquid electrolytes – a comparative study

ABSTRACT Electrodeposition of aluminium on the copper substrate using two different chloroaluminate ionic liquid electrolytes such as AlCl3/1-Butyl-3-methylimidazolium chloride electrolyte (AlCl3-BMIC) and AlCl3/1-Ethyl-3-methylimidazolium chloride electrolyte (AlCl3-EMIC) were studied. Cyclic voltammetry studies reveal the aluminium deposition process follows two steps mechanism in AlCl3-EMIC electrolytes and in AlCl3-BMIC electrolytes, it follows single-step mechanism. The AlCl3-EMIC electrolytes permit wide deposition current density window than the AlCl3-BMIC electrolytes for aluminium deposition with good properties. The aluminium deposits obtained from AlCl3-EMIC electrolyte have better surface properties than the deposits obtained from AlCl3-BMIC electrolyte. Detailed comparative studies of deposits obtained from these two electrolytes with respect to deposition mechanism, deposition efficiency and deposition current density window were done. The deposit properties such as surface morphology, microstructure and crystal structures were also compared. From this study, we observed the AlCl3-EMIC electrolyte gives good quality deposits than AlCl3-BMIC electrolyte.

A comprehensive assessment of heat loss mechanisms on the propagation of lean, premixed ethylene-oxygen flames in millimeter-scale tubes

Heat loss plays an important role on the flame propagation characteristics of premixed gas mixtures in small tubes. However, stringent spatial and temporal resolutions required to simulate these phenomena cause numerical investigations to resort to single-step global reaction mechanisms and ignore radiative losses. Both these restrictions are relaxed in this study where a skeletal 10-step mechanism and an optically thin radiation model are employed to study flame propagation in lean (Φ = 0.2) premixed ethylene/oxygen mixtures in millimeter-scale tubes (1 mm and 2 mm diameters). First, convergence in the spatial and temporal resolutions were ascertained and found to compare well with the characteristic reaction zone lengths and timescales determined from detailed reaction mechanisms. The accumulation of numerical errors over the simulation time frame was determined to be less than 0.06%. Radiative losses reduced the flame propagation velocities by 73% and 51% in the 1 mm diameter and 2 mm diameter tubes respectively and made the flames less concave. The flame velocities were moderately affected by the thermal boundary conditions (adiabatic versus isothermal walls). The radiant fractions were in the range 0.12–0.17. The slow CO oxidation reactions cause CO2 concentrations to be lower than those predicted from single-step mechanisms.