Acyclic Alkanes Research Articles

Rhodium(II)‐Catalyzed Selective C(sp3)−H Amination of Alkanes

AbstractThe development of an efficient catalytic system enabling the conversion of alkanes to valuable nitrogen‐containing building blocks is reported. Light alkanes can be selectively functionalized by an intermolecular C(sp3)−H amination reaction that proceeds at room temperature in the presence of only 1 mol % of a dirhodium(II) complex. Selective amination of tertiary C(sp3)−H within acyclic or cyclic alkanes used as limiting components leads to the corresponding amides isolated with yields in the 51–96 % range. The reaction, that can be performed on a gram‐scale, applies with equal levels of efficiency and selectivity to more complex hydrocarbons.

Solubility study of hydrogen in direct coal liquefaction solvent based on quantitative structure–property relationships model

Direct coal liquefaction (DCL) is an important and effective method of converting coal into high-value-added chemicals and fuel oil. In DCL, heating the direct coal liquefaction solvent (DCLS) from low to high temperature and pre-hydrogenation of the DCLS are critical steps. Therefore, studying the dissolution of hydrogen in DCLS under liquefaction conditions gains importance. However, it is difficult to precisely determine hydrogen solubility only by experiments, especially under the actual DCL conditions. To address this issue, we developed a prediction model of hydrogen solubility in a single solvent based on the machine-learning quantitative structure–property relationship (ML-QSPR) methods. The results showed that the squared correlation coefficient R2 = 0.92 and root mean square error RMSE = 0.095, indicating the model’s good statistical performance. The external validation of the model also reveals excellent accuracy and predictive ability. Molecular polarization (α) is the main factor affecting the dissolution of hydrogen in DCLS. The hydrogen solubility in acyclic alkanes increases with increasing carbon number. Whereas in polycyclic aromatics, it decreases with increasing ring number, and in hydrogenated aromatics, it increases with hydrogenation degree. This work provides a new reference for the selection and proportioning of DCLS, i.e., a solvent with higher hydrogen solubility can be added to provide active hydrogen for the reaction and thus reduce the hydrogen pressure. Besides, it brings important insight into the theoretical significance and practical value of the DCL.

The Formation of Small Amounts of Cyclopropane during Pulsed Pyrolysis of C4–C5 Acyclic Alkanes in the Adiabatic Compression Reactor

During high-temperature pulse pyrolysis of acyclic butanes and pentanes under adiabatic compression conditions, cyclopropane, a stressed cyclic hydrocarbon, was found among the reaction products in small quantities for the first time. The analysis of the reaction products was performed by gas chromatography using three capillary columns of different polarity, selectivity and sufficient efficiency. The identification of reaction products, including cyclopropane, was performed using retention times of individual substances and model mixtures, as well as comparing chromatograms with reference chromatograms from the literature and the ScanView Application Database. It was shown that the chromatographic peak attributed to cyclopropane could not be a ghost peak. Additional confirmation of this conclusion was obtained in a series of experiments on the pyrolysis of n-butane at a reduced initial temperature of the adiabatic compression reactor (from 120 °C to 50 °C) and a modified mode of GC analysis. Cyclopropane yields as a function of maximum temperature have a bell-shaped asymmetric dependence. The maximum value of the yield of cyclopropane increases with the transition from normal alkanes to isoalkanes, and from pentanes to butanes; for n-pentane, 0.009 wt. %, and for isobutene, ≈0.017 wt. %. During the pulse pyrolysis of isobutane, n-butane, isopentane and n-pentane, cyclopropane is not a primary product. Further theoretical and experimental studies are needed to establish the mechanism of cyclopropane formation during pyrolysis of C4–C5 acyclic alkanes.

Meteoric Water Incursion, Crude Oil Degradation and Calcite Cementation of an Upper Cretaceous Reservoir in the Zagros Foreland Basin (Kurdistan Region of Iraq)

Field observations, together with the results of gas chromatography–mass spectrometry (GC-MS) and stable carbon isotope analysis of bitumen, coupled with fluid inclusion microthermometry and stable isotope analyses of closely associated vug- and fracture-filling columnar calcite in the Upper Cretaceous Bekhme Formation, Kurdistan Region of Iraq, suggest that the degradation of crude oil was caused by the regional incursion of meteoric waters. This incursion, which is interpreted to have occurred during tectonic uplift during the Zagros Orogeny, is evidenced by: (i) the depletion of n-alkanes and acyclic isoprenoid alkanes (pristane and phytane) in the bitumen; (ii) low δ13CVPDB values (−8.5‰ to −3.9‰) and δ18OVPDB values (−22.9‰ to −15.0‰), with more radiogenic Sr isotopic ratios (0.70771–0.70772) compared to Cretaceous seawater; and (iii) low salinity and low temperatures (20 to 40 °C) in fluid inclusions of the columnar calcite. This study demonstrates that regional meteoric water incursion into sedimentary basins can be linked to crude oil degradation accompanied by calcite cementation events in carbonate reservoirs.

Degradation potential and pathways of methylcyclohexane by bacteria derived from Antarctic surface water

Cycloalkanes pose a tremendous environmental risk due to their high concentration in petroleum hydrocarbons and hazardous effects to organisms. Numerous studies have documented the biodegradation of acyclic alkanes and aromatic hydrocarbons. However, insufficient attention has been paid to studies on the microbial degradation of cycloalkanes, which might be closely linked to psychrophilic microbes derived from low-temperature habitats. Here we show that endemic methylcyclohexane (MCH, an abundant cycloalkane species in oil) consumers proliferated in seawater samples derived from the Antarctic surface water (AASW). The MCH-consuming bacterial communities derived from AASW exhibited a distinct species composition compared with their counterparts derived from other cold-water habitats. We also probed Colwellia and Roseovarius as the key active players in cycloalkane degradation by dilution-to-extinction-based incubation with MCH as sole source of carbon and energy. Furthermore, we propose two nearly complete MCH degradation pathways, lactone formation and aromatization, concurrently in the high-quality metagenome-assembled genomes of key MCH consumer Roseovarius. Overall, we revealed that these Antarctic microbes might have strong interactions that enhance the decomposition of more refractory hydrocarbons through complementary degradation pathways.

Atomic-level AI topological indices as efficient descriptors for developing predictive QSPR models for flash points of acyclic alkanes

Atomic-level AI topological indices as efficient descriptors for developing predictive QSPR models for flash points of acyclic alkanes

Online measurements of cycloalkanes based on NO+ chemical ionization in proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS)

Abstract. Cycloalkanes are important trace hydrocarbons existing in the atmosphere, and they are considered a major class of intermediate volatile organic compounds (IVOCs). Laboratory experiments showed that the yields of secondary organic aerosols (SOAs) from oxidation of cycloalkanes are higher than acyclic alkanes with the same carbon number. However, measurements of cycloalkanes in the atmosphere are still challenging at present. In this study, we show that online measurements of cycloalkanes can be achieved using proton transfer reaction time-of-flight mass spectrometry with NO+ chemical ionization (NO+ PTR-ToF-MS). Cyclic and bicyclic alkanes are ionized with NO+ via hydride ion transfer, leading to major product ions of CnH2n-1+ and CnH2n-3+, respectively. As isomers of cycloalkanes, alkenes undergo association reactions with major product ions of CnH2n ⚫ (NO)+, and concentrations of 1-alkenes and trans-2-alkenes in the atmosphere are usually significantly lower than cycloalkanes (about 25 % and <5 %, respectively), as a result inducing little interference with cycloalkane detection in the atmosphere. Calibrations of various cycloalkanes show similar sensitivities associated with small humidity dependence. Applying this method, cycloalkanes were successfully measured at an urban site in southern China and during a chassis dynamometer study of vehicular emissions. Concentrations of both cyclic and bicyclic alkanes are significant in urban air and vehicular emissions, with comparable cyclic alkanes / acyclic alkanes ratios between urban air and gasoline vehicles. These results demonstrate that NO+ PTR-ToF-MS provides a new complementary approach for the fast characterization of cycloalkanes in both ambient air and emission sources, which can be helpful to fill the gap in understanding the importance of cycloalkanes in the atmosphere.

Comparison of the United- and All-Atom Representations of (Halo)alkanes Based on Two Condensed-Phase Force Fields Optimized against the Same Experimental Data Set.

The level of accuracy that can be achieved by a force field is influenced by choices made in the interaction-function representation and in the relevant simulation parameters. These choices, referred to here as functional-form variants (FFVs), include for example the model resolution, the charge-derivation procedure, the van der Waals combination rules, the cutoff distance, and the treatment of the long-range interactions. Ideally, assessing the effect of a given FFV on the intrinsic accuracy of the force-field representation requires that only the specific FFV is changed and that this change is performed at an optimal level of parametrization, a requirement that may prove extremely challenging to achieve in practice. Here, we present a first attempt at such a comparison for one specific FFV, namely the choice of a united-atom (UA) versus an all-atom (AA) resolution in a force field for saturated acyclic (halo)alkanes. Two force-field versions (UA vs AA) are optimized in an automated way using the CombiFF approach against 961 experimental values for the pure-liquid densities ρliq and vaporization enthalpies ΔHvap of 591 compounds. For the AA force field, the torsional and third-neighbor Lennard-Jones parameters are also refined based on quantum-mechanical rotational-energy profiles. The comparison between the UA and AA resolutions is also extended to properties that have not been included as parameterization targets, namely the surface-tension coefficient γ, the isothermal compressibility κT, the isobaric thermal-expansion coefficient αP, the isobaric heat capacity cP, the static relative dielectric permittivity ϵ, the self-diffusion coefficient D, the shear viscosity η, the hydration free energy ΔGwat, and the free energy of solvation ΔGche in cyclohexane. For the target properties ρliq and ΔHvap, the UA and AA resolutions reach very similar levels of accuracy after optimization. For the nine other properties, the AA representation leads to more accurate results in terms of η; comparably accurate results in terms of γ, κT, αP, ϵ, D, and ΔGche; and less accurate results in terms of cP and ΔGwat. This work also represents a first step toward the calibration of a GROMOS-compatible force field at the AA resolution.

The Extraction Effect of Supercritical CO2 on Coal Organic Matter Based on CO2 Sequestration in Unmineable Coal Seam

On the basis of the effect of extraction components of supercritical CO2 (Sc-CO2) from coal on groundwater in the fields of greenhouse gas CO2 sequestration into deep and unmineable coal seams, Sc-CO2 extracts from coals were analyzed using GC/MS to investigate the compositions and their contents of the extracts under different experimental conditions. The results show that Sc-CO2 extracts from coals contain hydrocarbons and organic compounds containing heteroatoms. The main compound in the extract is hydrocarbons which include a large concentration of acyclic alkanes and alkenes and a small concentration of cycloalkanes and aromatic hydrocarbons. Even-numbered n-alkane dominates in the extract, and hexacosene is the main alkene in the extracts from lignite and bituminous coal. The aromatic hydrocarbons are more difficult to extract and their concentration decreases with the increase of coal rank. The main oxygen-containing compounds are esters and carboxylic acids which are more easily extracted from lignite. The concentrations of nitrogen-containing compounds are very small and are more difficult to extract from coal with the rank increase. A small concentration of sulfur-containing compounds is extracted from coal. The results demonstrate that Sc-CO2 has the potential to mobilize organic compounds from coal seams, which affect the transport of CO2 in coal seams and cause groundwater pollution.

A simple lattice projection method for estimating conformer strain energies using diamond or Lonsdaleite lattices to identify atomistic steric interactions and dihedral strain

A simple lattice projection method for estimating conformer strain energies using diamond or Lonsdaleite lattices to identify atomistic steric interactions and dihedral strain

Catalytic Asymmetric Diarylation of Internal Acyclic Styrenes and Enamides

Enantioselective transformations of olefins are among the most important strategies for the asymmetric synthesis of organic compounds. Chemo-, diastereo-, and stereoselective control of reactions with internal acyclic alkenes for the construction of functionalized acyclic alkanes still remain a persistent challenge. Here, we report a palladium-catalyzed asymmetric regiodivergent Heck-type diarylation of internal acyclic alkenes. The 1,2-diarylation of two accessible acyclic alkenes, cinnamyl carbamates and enamides with diazonium salts and aromatic boronic acids, furnishes products containing vicinal stereogenic centers via the stereospecific formation of carbonyl coordination-assisted transient palladacycles. Moreover, the asymmetric migratory diarylation of enamides enables the formation of incontiguous stereocenters by an interrupted diastereoselective 1,3-chain-walking process. This protocol streamlines access to highly functionalized multisubstituted enantioenriched carbamates and amine derivatives which are embedded in the key biologically active motifs.

Occurrence and distribution of cyclic-alkane-consuming psychrophilic bacteria in the Yellow Sea and East China Sea

Cyclic alkanes (c-alkanes) are toxic compounds that are abundant in subsurface oil reservoirs and spilled condensate; hence, their environmental risk is significant. Although numerous studies have focused on the decomposition of other compound classes, e.g., acyclic alkanes and aromatic hydrocarbons, very little is known about the biodegradation of c-alkanes in the marine environment. Here, we enriched methylcyclohexane (MCH)-degrading bacteria derived from the cold bottom water (10–20 °C) of China’s marginal seas in summer and characterized the changes to the bacterial community using high-throughput amplicon sequencing. MCH-consuming bacteria failed to grow from the warmer surface water (25–29 °C) in the same geographic sites and seasons. Notably, MCH-consuming communities derived from the cold bottom water in the Yellow Sea exhibit distinct structures compared to the other treatments. Furthermore, almost all dominant species in this setting appear to be specifically adapted to deeper cold water as indicated by significantly negative correlations to temperature (P < 0.01). From these results, we proposed that the biodegradation of MCH is effectively limited to the colder waters (10–20 °C) of China’s marginal seas, with uncultured psychrophiles acting as the key taxa for MCH decomposition. Overall, this study indicates key functions for uncultivated microbes in the marine environment.

Organic matter inputs and depositional palaeoenvironment recorded by biomarkers of marine‐terrestrial transitional shale in the Southern North China Basin

In recent years, significant breakthroughs have been achieved in shale gas exploration and exploitation of marine and continental shales in petroliferous basins of China. As an important petroliferous basin in China, marine–terrestrial transitional shale was widely distributed among the Southern North China Basin (SNCB). However, biomarkers distribution characteristics of marine–terrestrial transitional shale in the SNCB, which can reveal the organic matter inputs and paleoenvironmental characteristics, is not widely concerned. In general, organic matter in a transitional environment can be affected by the amounts of organic matters input from fresh water and aquatic organisms from the sea. To systematically investigate the organic geochemical characteristics of biomarkers in marine–terrestrial transitional shale from SNCB, core samples from the Upper Shihezi, Shanxi and Taiyuan formations were obtained from a single borehole in the SNCB. Gas chromatography–mass spectrometry (GC–MS) analysis was conducted on the saturated hydrocarbons. n‐Alkanes, acyclic isoprenoid alkanes, terpanes, and steranes were detected to study the change in organic matter inputs and sedimentary paleoenvironment of the marine–terrestrial transitional shale. The results reveal that organic matter inputs obviously changed during the sedimentary period in the study area of the SNCB. In addition, the terrestrial higher plants contributed more organic matter to shale from the Upper Shihezi Formation compared to the Taiyuan Formation and the Shanxi Formation. The shift of organic matter inputs is consistent with marine regression in the Early Permian period, which may significantly influence the organic matter input characteristics. Meanwhile, the marine–terrestrial transitional shale, including samples from the Taiyuan, Shanxi and Upper Shihezi formations, was deposited in a relatively oxic condition during the depositional process.

A comprehensive study on low-temperature oxidation chemistry of cyclohexane. I. Conformational analysis and theoretical study of first and second oxygen addition

To understand the low-temperature oxidation chemistry of cyclohexane, conformational analysis and theoretical study of the first and second oxygen addition are performed using quantum chemical calculations and kinetic calculations. Pressure- and temperature-dependent rate constants and branching ratios for major reaction channels are determined with RRKM/master-equation simulations over 298–2000 K and 0.01–1000 bar. The theoretical results indicate that the rapid inversion-topomerization processes facilitate fast equilibrium between axial and equatorial conformers. This can greatly counterbalance the influence of initial positions of side-chain groups in ROO, QOOH, cis-OOγQOOH and trans-OOγQOOH conformers. Conformational effects are found to be influential on the chain branching reaction sequences in second oxygen addition. The carbon ring prevents the conventional intramolecular H-transfer of cis-OOγQOOH conformers to yield ketohydroperoxides, as well as the inversion-topomerization from cis-OOγQOOH conformer to trans-OOγQOOH conformers. cis-OOγQOOH conformers mainly undergo alternative isomerization channel (cis-OOγQOOH→γP(OOH)2→alkenylhydroperoxides+OH→oxy radical+OH+OH), while trans-OOγQOOH conformers have both conventional isomerization channel (trans-OOγQOOH→ketohydroperoxides+OH→oxy radical+OH+OH) and alternative isomerization channel (trans-OOγQOOH→γP(OOH)2→alkenylhydroperoxides+OH→oxy radical+OH+OH). Kinetic calculation results also support the application of the thumb rule widely used in acyclic alkane oxidation that the rate constant of QOOH+O2 is roughly half of that of R+O2 in cyclic alkane oxidation, while it is indicated that estimating the rate constants of OOQOOH reactions from similar reactions of ROO may cause significant uncertainties.

Graph Theoretical Atom-Type-Based Descriptors for Structural Characterization and Retention Prediction of Acyclic Alkanes

Graph Theoretical Atom-Type-Based Descriptors for Structural Characterization and Retention Prediction of Acyclic Alkanes

Systematic optimization of a fragment-based force field against experimental pure-liquid properties considering large compound families: application to oxygen and nitrogen compounds.

The CombiFF approach is a workflow for the automated refinement of force-field parameters against experimental condensed-phase data, considering entire classes of organic molecules constructed using a fragment library via combinatorial isomer enumeration. One peculiarity of this approach is that it relies on an electronegativity-equalization scheme to account for induction effects within molecules, with values of the atomic hardness and electronegativity as electrostatic parameters, rather than the partial charges themselves. In a previous article [M. P. Oliveira, M. Andrey, S. R. Rieder, L. Kern, D. F. Hahn, S. Riniker, B. A. C. Horta and P. H. Hünenberger, J. Chem. Theory. Comput. 2020, 16, 7525], CombiFF was introduced and applied to calibrate a GROMOS-compatible united-atom force field for the saturated acyclic (halo-)alkane family. Here, this scheme is employed for the construction of a corresponding force field for saturated acyclic compounds encompassing eight common chemical functional groups involving oxygen and/or nitrogen atoms, namely: ether, aldehyde, ketone, ester, alcohol, carboxylic acid, amine, and amide. Monofunctional as well as homo-polyfunctional compounds are considered. A total of 1712 experimental liquid densities ρliq and vaporization enthalpies ΔHvap concerning 1175 molecules are used for the calibration (339 molecules) and validation (836 molecules) of the 102 non-bonded interaction parameters of the force field. Using initial parameter values based on the GROMOS 2016H66 parameter set, convergence is reached after five iterations. Given access to one processor per simulated system, this operation only requires a few days of wall-clock computing time. After optimization, the root-mean-square deviations from experiment are 29.9 (22.4) kg m−3 for ρliq and 4.1 (5.5) kJ mol−1 for ΔHvap for the calibration (validation) set. Thus, a very good level of agreement with experiment is achieved in terms of these two properties, although the errors are inhomogeneously distributed across the different chemical functional groups.

Compound-specific δ2H and δ13C values of n-alkanes as a tool to unravel complex petroleum mixtures in the South Viking Graben, Norway

In order to resolve oil mixtures and for oil-source correlation purposes, both hydrogen (δ2H) and carbon isotope compositions (δ13C) of n-alkanes and acyclic isoprenoid alkanes have been determined in petroleum mixtures and extracts from Jurassic source rocks of distinct organic matter type, depositional setting and lithology in the South Viking Graben, Norway. δ2H values vary from −80 to −140‰ for n-alkanes and from −130 to −165‰ for pristane (Pr) and phytane (Ph) in oil and condensate samples. At the same maturity level, in the main oil generative window, individual n-alkanes from most oils and condensates show a 2H-enrichment with n-alkane chain length by 15 to 50‰. With the increase in the estimated input of hydrocarbons from terrigenous source material to petroleum mixtures, the n-alkanes (>C20) exhibit a higher 2H-enrichment while n-alkanes (C10-C14) show a higher 13C-enrichment. δ2H values of n-alkanes (>C20) are useful to discriminate mixed oils that were not well differentiated by δ13C data. δ2H values of individual n-alkanes from oils suggest a possible exchange of C-bound H with other hydrogen during their generation from precursor molecules. We find that δ2H values of n-alkanes from Jurassic source rock extracts, at the onset of oil generation, were mainly controlled by the isotopic composition of biosynthetic precursors and varied from −100 to −150‰. Combination of carbon and hydrogen isotope compositions of n-alkanes proved to be a useful tool to discriminate Jurassic petroleum mixtures from distinct sources in the Norwegian South Viking Graben.

Geochemistry of neoprotherosoic organic matter in the southeast of the Siberian platform

In the Neoproterozoic of the Aldan-Maya depression, the rocks of the Malgin (MF), Tsipanda (TF) and Kumakha (KF) Formations are enriched in organic matter (OM) and can be classified as source rocks. High generation potential is typical for the MF and TF (267–511 mg HC/g TOC). The thermal maturity level of OM corresponds to MC12 grade (Tmax is 438–443ºC). Based on the biomarker distribution, the biological precursors of OM in these formations are mostly prokaryotes, including cyanobacteria (hopanes, acyclic biomarkers) and to a lesser extent eukaryotes (the presence of steranes С27-C30) that lived in the Precambrian (the presence of 12- and 13-monomethylalkanes) marine (absence of continental biomarkers, the distributions of acyclic alkanes and steranes) basin with clayey sedimentation (high content of diasteranes). The absence of steranes in some samples (the absence of eukaryotes in the source OM), the MF is likely to have been partly deposited before the emergence of eukaryotes. Most samples have elevated concentrations of low-molecular tricyclanes (2C19-20/C23-26&gt;1), which can be attributed to the specificity of the source biota, although it is not typical for marine OM. A rare homologous series of 2,7-dimethylalkanes that has been recently found by other researchers in some Precambrian strata is present in several samples of the MF and KF and totally absent from all samples of the TF. This may indicate the differences in its biota, depositional environments or its evolution during diagenesis and catagenesis. A distinctive feature of the TF is the high content of ethylcholestanes (C29/C27=2.5).

DFT исследование триплетных и синглетных элементарных актов окисления ациклических и циклических алканов, инициированных первичным взаимодействием с 3O2

The primary oxidation stages of 3O2 model acyclic and cyclic alkanes and their subsequent triplet and singlet elementary events were studied for the first time by the DFT method with the density functional B3LYP and basis set 6-311++g(df,p). According to quantum chemical DFT calculations the C–H radical cleavage of the bonds of acyclic and cyclic alkanes upon interaction with 3O2 is almost completely thermodynamically shifted toward the initial state of the reaction system. This energy of primary oxidizing events explains the extremely low reactivity of saturated alkanes in comparison with asphaltene structural fragments under the conditions of SCF technology for the extraction of heavy oils and asphaltenes by a propane-butane mixture. It has been demonstrated that for all elementary acts of primary alkane oxidation the product of the direct reaction direction is not a free pair of radicals but a triplet hydrogen complex with a pronounced hydrogen bond between the hydroperoxyl radical and the radical form of the corresponding hydrocarbon. A new, previously not taken into account very exothermic (H = -29.25 – -30.77 kcal/mol) reaction direction is described which corresponds to triplet recombination of alkyl radicals and a hydroperoxyl radical in its oxygen-concentrated part. The products of this recombination are triplet forms of alkane hydroperoxides in which there is a fairly loosened triplet O---O bond with a length of 2.20-2.23 Å, which is ~0.72-0.77 Å more than bond length in the singlet state.

Pressure-dependent rate rules for intramolecular H-migration reactions of normal-alkyl cyclohexylperoxy radicals

For hydrocarbon fuels, reliable chemical mechanisms play an essential role towards improving the simulations of combustion process. However, in most of the previous modeling studies for alkylcycloalkanes combustion, the kinetic parameters are taken from acyclic alkanes based on the similarities between the reaction classes of alkylcycloalkanes and acyclic alkanes. Among the reaction families for alkylcycloalkanes, the intramolecular H-migration reactions of normal-alkyl cyclohexylperoxy radicals are one of the most important reaction families in the low temperature oxidation mechanisms. High-pressure limit rate rules and pressure-dependent rate rules for this reaction family have been developed based on quantum chemical computations at the CBS-QB3 level in combination with the transition state theory (TST) and Rice–Ramsberger–Kassel–Marcus/Master-Equation (RRKM/ME) theory. The reactions in this family involve a bicyclic transition state and can be divided into classes depending upon the cycle size of the newly formed cycle in the transition states and the types of the carbons from which the H atoms are migrated and if the H-migration occurs on the alkyl side chain, or on the cycle, or from the side chain to the cycle, or from the cycle to the side chain. For each reaction class, a representative set of reactions are chosen from methylcyclohexane to n-butylcyclohexane and the energy barriers of all chosen reactions are calculated and the average value for each class is obtained and compared with the value of the similar reaction class in alkanes. The high-pressure limit rate constants and the pressure-dependent rate constants of all reactions at pressures varying from 0.01 to 100 atm are calculated and the high-pressure limit rate rules and pressure-dependent rate rules for each class are derived from the average rate constants of reactions within each class. All calculated rate constants are fitted by a nonlinear least-squares method to the form of a modified Arrhenius rate expression.It is shown that there are large differences of the rate constants between alkylcycloalkanes and alkanes no matter if the H-migration occurs on the alkyl side chain, on the cycle or between the side chain and the cycle. Therefore, the construction of rate rules for alkylcycloalkanes, instead of taking values from similar reactions in alkanes, is necessary and significant to the low-temperature combustion modeling of alkylcyclohexanes.