G3B3 Method Research Articles

Prediction of the pKa's of Hydrated Metal Carbonates and Bicarbonates for Mg, Ca, Mn, Fe, Co, Ni, Cu, and Zn Dications.

The gas- and aqueous-phase acidities of hydrated metal dication carbonates, bicarbonates, and hydroxide complexes M(CO3)(H2O)n for n = 1 to 3, M(HCO3)2, M(HCO3)2(H2O)2, M(HCO3)(OH), and M(HCO3)(H2O)2(OH) for M = Mg, Ca, Mn, Fe, Co, Ni, Cu, and Zn were calculated at the CCSD(T)/aug-cc-pwCVDZ/cc-pwCVDZ level in the gas phase and at the B3LYP/aug-cc-pVTZ/cc-pVTZ(-PP) level with the COSMO self-consistent reaction field (SCRF) method in the aqueous phase. The composite correlated molecular orbital theory G3(MP2) and G3(MP2)B3 methods were used to predict the pKa's of the Mg structures and cis-cis carbonic acid to provide additional benchmarks. Using values scaled to experiment for H2CO3, the pKa's of bicarbonate ligands in group 2 and transition-metal complexes were compared to carbonic acid to gauge the effect of the metal complex on the bicarbonate. The group 2 metal complexes M(HCO3)2 and M(HCO3)(OH) decreased the acidity of the bicarbonate ligands, whereas their dihydrates were even less acidic. The transition-metal di-bicarbonate and bicarbonate hydroxide complexes generally made the bicarbonate more acidic especially when reduction of the metal occurs consistent with electron donation from the ligands; this is accompanied by spin transfer which typically increases in the order Mn < Fe < Co < Ni < Cu. The transition-metal dihydrates were less acidic than carbonic acid. Using values scaled to experiment for hydrated metal dications, the pKa's of water coordinated to group 2 and transition-metal complexes were generally more acidic than the hydrated metal dications, with the exception of Ca bicarbonate dihydrate, Co carbonate, Ni di-bicarbonate dihydrate, and Cu bicarbonate hydroxide di-bicarbonate.

Theoretical calculation of the adiabatic electron affinity and vertical electron affinity of some hydantoin drugs

Several DFT approaches with 6–311 + G(2df,2p) basis set at the B3LYP/6–31 + G(d,p) geometries were examined to calculate accurate adiabatic electron affinity (AEA) for some hydantoin derivatives. The accuracy of these approaches was statistically examined with respect to the standard reference AEA, which obtained by using G4, G3B3 and CBS-QB3 methods. The results reveal that the least RMSE values were obtained for B3PW91, TPSSTPSS and B3LYP approaches, respectively. The B3PW91 approach in conjunction with the 6–311 + G(2df,2p) basis set at the B3LYP/6–31 + G(d,p) geometries were used to calculate the AEA for some hydantoin drugs, including Phenytoin, Nitrofurantoin, Allantoin, Iprodine, Ethotoin and Mephenytoin, as well as some of phenytoin and nitrofurantoin derivatives. Moreover, the vertical electron affinity (VEA) of all investigated compounds were calculated using the B3LYP/6–31 + G(d,p) level. The substitution effects on the AEA values were studied and discussed. The results reveal that the electron donating groups decrease the AEA and VEA value, whereas, the reverse is true in the case of the electron withdrawing groups. Furthermore, NBO analysis was used to calculate the natural spin density and atomic charges of the neutral and anion species. The results obtained show, in general, that the maximum spin density is located on the carbonyl carbon atom of the hydantoin ring. The changes in the geometrical structures (bond lengths and bond angles) of anions compared to the neutral molecules were also studied and discussed. Correlations between the AEA and VEA with the energy gap with the correlation coefficients (R2) close to unity were shown. Furthermore, the AEA and VEA for some hydantoin derivatives and drugs were also calculated in aqueous solution, and their results are compared with the gas phase results.

Theoretical calculation of the adiabatic electron affinities of the monosubstituted benzaldehyde derivatives

In the current study, several computational models were examined to calculate accurate adiabatic electron affinity (AEA) of twelve m- and p-monosubstituted benzaldehyde derivatives. The examined models are as follows: (i) composite high-level ab initio (G3B3, G4, CBS-Q, and CBS-QB3), (ii) Three hybrid DFT approaches (B3LYP, CAM-B3LYP, and wB97XD) with two basis sets (6–31 + G(d,p) and 6–311++G(2df,2p)) and (iii) single point calculation using fifteen DFT approaches with 6–311++G(2df,2p) at the B3LYP/6–31 + G(d,p) geometry. Several statistical descriptors were computed to validate the calculated AEAs based on the available experimental results. Results revealed that G3B3 and CBS-QB3 are the most accurate result, while G4 and CBS-Q methods yield less accurate ones. Also, the wB97XD and CAM-B3LYP in combination with 6–311++G(2df,2p) able to calculate accurate AEAs. Low CPU time single point calculation strategy by using wb97 and wb97X approaches can compute AEAs value as accurately as G3B3 and CBS-QB3 methods. The AEAs of other several monosubstituted benzaldehydes were also predicted by using the wb97, wb97X, and wb97XD. The effect of the nature and position of substituents on the natural spin density and natural charge is also studied and discussed.

Evaluating the Atmospheric Loss of H2 by NO3 Radicals: A Theoretical Study

Molecular hydrogen (H2) is now considered among the most prominent substitute for fossil fuels. The environmental impacts of a hydrogen economy have received more attention in the last years, but still, the knowledge is relatively poor. In this work, the reaction of H2 with NO3 radical (the dominant night-time detergent of the atmosphere) is studied for the first time using high-level composite G3B3 and modification of high accuracy extrapolated ab initio thermochemistry (mHEAT) methods in combination with statistical kinetics analysis using non-separable semi-classical transition state theory (SCTST). The reaction mechanism is characterized, and it is found to proceed as a direct H-abstraction process to yield HNO3 plus H atom. The reaction enthalpy is calculated to be 12.8 kJ mol−1, in excellent agreement with a benchmark active thermochemical tables (ATcT) value of 12.2 ± 0.3 kJ mol−1. The energy barrier of the title reaction was calculated to be 74.6 and 76.7 kJ mol−1 with G3B3 and mHEAT methods, respectively. The kinetics calculations with the non-separable SCTST theory give a modified-Arrhenius expression of k(T) = 10−15 × T0.7 × exp(−6120/T) (cm3 s−1) for T = 200–400 K and provide an upper limit value of 10−22 cm3 s−1 at 298 K for the reaction rate coefficient. Therefore, as compared to the main consumption pathway of H2 by OH radicals, the title reaction plays an unimportant role in H2 loss in the Earth’s atmosphere and is a negligible source of HNO3.

Calculation of vertical and adiabatic ionization potentials for some benzaldehydes using hybrid DFT, multilevel G3B3 and MP2 methods

The adiabatic ionization potential (AIP) and vertical ionization potential (VIP) for eight benzaldehydes were calculated using DFT (B3LYP, CAM-B3LYP and ωB97XD), MP2, G3B3 and CBS-QB3 methods. Basis set dependence was checked using four different basis sets 6-311G(d,p), 6-31+G(d,p), 6-311++G(2df,2p) and cc-pVTZ. Computed results were compared with the experimental data. Error metrics and statistical tools were used to validate the methods tested. Results showed an excellent agreement between the computed results and the experimental ones. Nature of the substituted groups and solvent effect on AIP values were investigated. Changes in the geometrical structures of cationic species were compared with neutral ones.

Sustainable hydrogen storage: Thermochemistry of amino-alcohols as seminal liquid organic hydrogen carriers

Amino-alcohols are considered for sustainable hydrogen storage systems based on catalytic peptide formation. Experimental and theoretical thermochemical studies of amino-alcohols have been performed, including vapour pressure measurements, combustion calorimetry, and quantum-chemical calculations. The standard molar enthalpies of vaporization of amino-alcohols were calculated from the temperature dependence of the vapour pressures measured by the transpiration method. Energies of combustion for six amino-alcohols were measured using the high-precision combustion calorimetry. The available in the literature primary data on vapour pressures, enthalpies of vaporization, and enthalpies of formation of amino-alcohols were collected and evaluated. The experimental standard molar gas-phase enthalpies of formation of amino-alcohols were derived from the evaluated results. The high-level G3B3, G3MP2, and G4 quantum-chemical methods were used to establish consistency of the experimental and theoretical results. The surprisingly low enthalpy of reaction of the reversible dehydrogenation of 2-amino-ethanol, calculated from the experimental data, makes this liquid organic hydrogen carrier system (LOHC) promising for further optimization and development.

Thermal Degradation and Bimolecular Decomposition of 2-Ethoxyethanol in Binary Ethanol and Isobutanol Solvent Mixtures: A Computational Mechanistic Study.

A thorough computational study of a thermal degradation mechanism of 2-ethoxyethanol (2-EE) in the gas phase has been implemented using G3MP2 and G3B3 methods. The stationary point geometries were optimized at the B3LYP functional utilizing the 6-31G(d) basis set. Intrinsic reaction coordinate analysis was performed to determine the transition states on the potential energy surfaces. Nineteen primary different reaction mechanisms, along with the kinetic and thermodynamic parameters, are demonstrated. Most of the thermal degradation mechanisms result in a concerted transition state step as an endothermic process. Among 11 degradation pathways of 2-ethoxyethanol, the formation of ethylene glycol and ethylene is kinetically significant with an activation energy of 269 kJ mol–1 at the G3B3 method. However, the kinetic and thermodynamic calculations indicate that ethanol and ethanal’s formation is the most plausible reaction with an activation barrier of 287 kJ mol–1 at the G3B3 method. For the bimolecular dissociation reaction of 2-ethoxyethanol with ethanol, the pathway that produces ether, H2, and ethanol is more likely to occur with a lower activation energy of 221 kJ mol–1 at the G3B3 method. Thus, 2-EE has experienced a set of complex unimolecular and bimolecular reactions.

Benchmark calculations of proton affinity and gas-phase basicity using multilevel (G4 and G3B3), B3LYP and MP2 computational methods of para-substituted benzaldehyde compounds.

This study presents the benchmark calculations of proton affinities (PAs) and gas-phase basicities (GBs) of 8-para substituted benzaldehyde compounds using the multilevel model chemistries (G3B3 and G4), density-functional quantum model (B3LYP) and ab initio model (MP2). The results show that the computed properties are strongly correlated with the available experimental data. The PAs and the GBs of other eight para-substituted benzaldehyde compounds, for which the experimental data does not currently exist, have been calculated using G3B3 and B3LYP methods. The correlations between the experimental PAs and GBs with the computed properties such as PA, GB, chemical properties (bond lengths, electron density and δ1 H NMR chemical shift) of the investigated benzaldehydes have been studied and statistically analyzed. The influence of the substituted groups has been discussed in terms of inductive effect and electron donating and electron withdrawing effect. The results obtained show that the chemical properties of the benzaldehyde compounds are controlled by the strong coupling between the CHO group and the nature of the para-substituent groups through the benzene ring as a conducting linkage.

Investigation of vacuum ultraviolet photoionization of methylcyclohexane in energy region of 9−15.5 eV

Vacuum ultraviolet (VUV) photoionization and photodissociation of methylcyclohexane have been studied utilizing a reflectron time-of-flight mass spectrometer (RTOF-MS) with synchrotron radiation source. Photoionization efficiency curves (PIEs) of molecule ion C7H14+ and fragment ions C7H13+, C6H11+, C6H10+, C5H10+, C5H9+, C4H8+, C4H7+, and C3H5+ were observed. The ionization energy of methylcyclohexane was measured to be (9.80±0.03) eV, and appearance energies of fragment ions were determined from the PIEs. Optimized structures of transitional states, intermediates and product ions were characterized at the B3LYP/6-31G(d) level and the energies were calculated using G3B3 method. Formation channels of dominating fragment ions were proposed. Intramolecular hydrogen migrations and carbon ring-opening were the foremost processes in fragmentation pathways of methylcyclohexane.

Benchmark study of popular density functionals for calculating binding energies of three-center two-electron bonds.

Density functional theory (DFT) can be used to study the three-center two-electron (3c2e) bonding mode, which is universal in catalysts containing alkaline-earth (Ae) and boron-group (Bg) elements. However, because of the delocalization pattern of the 3c2e bond, the wavefunction cannot be accurately described by DFT methods. The calculated energies of Ae and Bg catalysts therefore fluctuate greatly when different functionals are used, largely because of inconsistent DFT-calculated binding energies of 3c2e bonds. Nevertheless, with the development of supercomputers and theoretical calculation software, the DFT method is becoming increasingly popular for studying Ae and Bg catalysts. In this study, we compared the performances of 21 functionals with the high-level composite G3B3 method in calculations for the binding energies of 3c2e bonds. Several frequently used post-Hartree-Fock methods were also tested. The calculation results indicate that the M06-2X, MN12-L, and MN15 functionals give consistent and reliable binding energies for common 3c2e bonds. © 2018 Wiley Periodicals, Inc.

High level ab initio thermochemistry of SF5OOO radical

The molecular structure, vibrational frequencies, and enthalpy of formation of SF5OOO radical have been examined using several functionals such as pure GGA, hybrid GGA, meta-GGA, and “double hybrid” from density functional theory (DFT). The results show the existence of three conformations with symmetries Cs′, Cs and C1 for the SF5OOO radical, each differing in the spatial distribution and interactions of the oxygen atoms. All the functionals used in this study were capable of predicting the experimental vibrational frequencies, albeit with small differences in some of the vibrational bands. The thermochemistry studies were carried out with high-level Gn theories (G3MP2B3, G3B3, G4MP2 and G4), which provided reliable enthalpies of formation of −218.3 ± 1.3, −217.2 ± 1.6, and −218.0 ± 1.5 kcal mol−1 for SF5OOO (Cs), SF5OOO (Cs′) and SF5OOO (C1) at 298 K. The relative stability of the three conformations was found to be almost identical with interconversion barriers at 0 K less than lower 1 kcal mol−1. Finally, application of bond additivity corrections (BAC) to the G3MP2B3 and G3B3 methods made the enthalpy of formation converge to the values obtained with the G4MP2 and G4 methods.

Performance of Density-Functional Tight-Binding in Comparison to Ab Initio and First-Principles Methods for Isomer Geometries and Energies of Glucose Epimers in Vacuo and Solution.

Density functional theory (DFT) is a widely used methodology for the computation of molecular and electronic structure, and we confirm that B3LYP and the high-level ab initio G3B3 method are in excellent agreement for the lowest-energy isomers of the 16 glucose epimers. Density-functional tight-binding (DFTB) is an approximate version of DFT with typically comparable accuracy that is 2 to 3 orders of magnitude faster, therefore generally very suitable for processing large numbers of complex structures. Conformational isomerism in sugars is well known to give rise to a large number of isomer structures. On the basis of a comprehensive study of glucose epimers in vacuo and aqueous solution, we found that the performance of DFTB is on par to B3LYP in terms of geometrical parameters excluding hydrogen bonds and isomer energies. However, DFTB underestimates both hydrogen bonding interactions as well as torsional barriers associated with rotations of the hydroxy groups, resulting in a counterintuitive overemphasis of hydrogen bonding in both gas phase as well as in water. Although the associated root mean squared deviation from B3LYP within epimer isomer groups is only on the order of 1 kcal/mol, this deviation affects the correct assignment of major isomer ordering, which span less than 10 kcal/mol. Both second- as well as third-order DFTB methods are exhibiting similar deviations from B3LYP. Even after the inclusion of empirical dispersion corrections in vacuum, these deviations remain for a large majority of isomer energies and geometries when compared to dispersion-corrected B3LYP.

Elucidating the Trends in Reactivity of Aza‐1,3‐Dipolar Cycloadditions

This report describes a density functional theory investigation into the reactivities of a series of aza‐1,3‐dipoles with ethylene at the BP86/TZ2P level. A benchmark study was carried out using QMflows, a newly developed program for automated workflows of quantum chemical calculations. In total, 24 1,3‐dipolar cycloaddition (1,3‐DCA) reactions were benchmarked using the highly accurate G3B3 method as a reference. We screened a number of exchange and correlation functionals, including PBE, OLYP, BP86, BLYP, both with and without explicit dispersion corrections, to assess their accuracies and to determine which of these computationally efficient functionals performed the best for calculating the energetics for cycloaddition reactions. The BP86/TZ2P method produced the smallest errors for the activation and reaction enthalpies. Then, to understand the factors controlling the reactivity in these reactions, seven archetypal aza‐1,3‐dipolar cycloadditions were investigated using the activation strain model and energy decomposition analysis. Our investigations highlight the fact that differences in activation barrier for these 1,3‐DCA reactions do not arise from differences in strain energy of the dipole, as previously proposed. Instead, relative reactivities originate from differences in interaction energy. Analysis of the 1,3‐dipole–dipolarophile interactions reveals the reactivity trends primarily result from differences in the extent of the primary orbital interactions.

Ideal gas thermochemical properties of silicon containing inorganic, organic compounds, radicals, and ions

AbstractThe ideal gas thermochemical properties such as standard heat of formation, entropy, and heat capacities of 112 inorganic and 35 organic neutral compounds, radicals, and ions containing silicon were calculated using molecular properties obtained with the G3B3 (or G3//B3LYP) method. Among them were linear and cyclic silanes, silenes, hydrocarbonsilanes, fluorine, and oxygen containing compounds. Many of their molecular and thermodynamic properties were calculated for the first time and 16 of them had no CAS number.Additionally the thermochemical properties were presented in the NASA 7 term polynomial format for the temperature range of 200‐6000 K commonly used in chemical kinetic modeling and simulation programs. The polynomials are available in the Supporting Information supplement to this article free of charge.

Atmospheric Reaction of Cl with 4-Hydroxy-2-pentanone (4H2P): A Theoretical Study.

The kinetics and the mechanism of the reaction of 4-hydroxy-2-pentanone (4H2P) with Cl atom were investigated using quantum theoretical calculations. Density functional theory, CBS-QB3, and G3B3 methods are used to explore the reaction pathways. Rice-Ramsperger-Kassel-Marcus theory is employed to obtain rate constants of the reaction at atmospheric pressure and the temperature range 278-400 K. This study provides the first theoretical and kinetic determination of Cl rate constant for reactions with 4H2P over a large temperature range. The obtained rate constant 1.47 × 10-10 cm3 molecule-1 s-1 at 298 K is in reasonable agreement with those obtained for C4-C5 hydroxyketones both theoretically and experimentally. The results regarding the structure-reactivity relationship and the atmospheric implications are discussed.

Carbon dioxide capture by planar (AlN)n clusters (n=3-5).

Searching for materials and technologies of efficient CO2 capture is of the utmost importance to reduce the CO2 impact on the environment. Therefore, the (AlN)n clusters (n=3-5) are researched using density functional theoretical calculations. The results of the optimization show that the most stable structures of (AlN)n clusters all display planar configurations at B3LYP and G3B3 methods, which are consistent with the reported results. For these planar clusters, we further systematically studied their interactions with carbon dioxide molecules to understand their adsorption behavior at the B3LYP/6-311+G(d,p) level, including geometric optimization, binding energy, bond index, and electrostatic. We found that the planar structures of (AlN)n (n=3-5) can capture 3-5 CO2 molecules. The result indicates that (AlN)n (n=3-5) clusters binding with CO2 is an exothermic process (the capture of every CO2 molecule on (AlN)n clusters releases at least 30kcal mol-1 in relative free energy values). These analysis results are expected to further motivate the applications of clusters to be efficient CO2 capture materials.

Dissociative Photoionization of 1,4-Dioxane with Tunable VUV Synchrotron Radiation

The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy region of 8.0–15.5 eV. Parent ion and fragment ions at m/z 88, 87, 58, 57, 45, 44, 43, 41, 31, 30, 29, 28 and 15 are detected under supersonic conditions. The ionization energy of DX as well as the appearance energies of its fragment ions C4H7O2+, C3H6O+, C3H5O+, C2H5O+, C2H4O+, C2H3O+, C3H5+, CH3O+, C2H6+, C2H5+/CHO+, C2H4+ and CH3+ was determined from their photoionization efficiency curves. The optimized structures for the neutrals, cations, transition states and intermediates related to photodissociation of DX are characterized at the B3LYP/6-31+G(d,p) level and their energies are obtained by G3B3 method. Possible dissociative channels of the DX are proposed based on comparison of experimental AE values and theoretical predicted ones. Intramolecular hydrogen migrations are found to be the dominant processes in most of the fragmentation pathways of 1,4-dioxane.

Polycyclic Aromatic Hydrocarbon Growth by Diradical Cycloaddition/Fragmentation.

The recent theoretical and experimental investigations on the growth of polycyclic aromatic hydrocarbons in pyrolytic environments highlight the possible role of the 1,4-cycloaddition/fragmentation (1,4-CAF) steps in the formation of PAH intermediates and consequently soot. The present theoretical study explores the possibility to generalize such mechanism to reactions involving various diradical compounds and stable multiring structures. The calculations were performed using the uB3LYP/6-311G(d,p) method and different composite methods, when possible, for more accurate energy estimates. First, the complex potential energy surface for the reactions between o-benzyne and naphthalene was investigated, including the 1,4-CAF mechanism to form anthracene and acetylene through the dibenzobicyclo[2.2.2]octatriene intermediate. Moreover, the products of the addition reactions to the α- and β-carbons and to the ring-junction atoms were determined. The energies for the optimized CAF structures, which constitute the most-favorable pathway from an energetic point of view, were calculated using CBS-QB3, G3(MP2)B3, and G3B3 methods and compared to the corresponding values for the o-benzyne + benzene reactions. Additional calculations were focused on the possible CAF reactions between o-benzyne and larger multiring structures, such as anthracene, phenanthrene, pyrene, and the four-ring PAHs. The results indicate how the energetics of such reactions is influenced by both the size of the PAH compound and the position of the carbon atoms involved. In the second part of the study, the energy barriers necessary to form multiring diradicals from the corresponding radical molecules were analyzed at a G3(MP2)B3 level of theory. Such calculations are preliminary for the subsequent study on the CAF reactions between the different diradical intermediates and benzene. While the size of the diradical does not affect significantly the energy barriers, the position of the diradical site is critical. The concerted Diels-Alder reactions between the naphthynes and naphthalene were also studied in order to further clarify the analogies between the reactions involving different diradicals. Based on these results, kinetic considerations were provided based on the comparison with the simpler o-benzyne + benzene system, although further higher-level calculations and master equation kinetic analyses will be required to derive the general kinetic rules.

Theoretical study on the mechanism of the N2H4 plus O2 reaction on the singlet and triplet potential energy surfaces

Kinetic and mechanism of atmospheric reaction of hydrazine (N2H4) and molecular oxygen (O2) on the singlet and triplet potential energy surfaces have been investigated in details using ab initio and DFT methods. All stationary points involved in the title reaction were optimized at the B3LYP, MP2 and G3B3 methods of computation in connection with the 6-311++G (3df, 3pd) basis set. For calculation of accurate energies, the CCSD(T) method is applied. Also, thermodynamic parameters and rate constant are calculated at M06-2x method with the mentioned basis set. The results show that direct hydrogen abstraction mechanism is the most important pathways of reaction. Three pre-reactive complexes, 1C1, 1C2, 3C1, on the singlet and triplet potential energy surfaces were formed between hydrazine and molecular oxygen. Seven different products are suggested which all of them have enough thermodynamic stability. The production of HNNH+H2O2 and H2N2(OH)2 are the main reaction channels in thermodynamic viewpoint with standard Gibbs free energy of ∆G0=−41.9 and −54.1kcal/mol at M06-2x level, respectively. In kinetic point of view, H2NN+H2O2 adduct (on singlet state) and 2N2H3+2HO2 adducts (on singlet and triplet states) after passing one corresponding low level transition state are the most favor pathways of reaction. In this reaction, N2H3+HO2 adducts in singlet and triplet states are the main kinetically products. So, the rate constants are calculated at the 300–2500K temperature range for the reliable pathway of the mentioned adducts in both states at M06-2X/6-311++(3df, 3pd) method.

The Ideal Gas Thermochemistry of Oxonium Cations

The ideal gas thermochemistry of 20 carbon oxonium cations were calculated for the first time using the DFT G3B3 method. The cations are CH–OH2+, CH2–OH2+, CH3–OH2+, CH3O═CH2+, [CH2–CH2]OH+, CH3OH–CH2+, (CH3)2OH+, (CH3)3O+, n-C3H7OH2+, (CH3)2CHOH2+, (CH3)2OCH2+, CH3[CH–CH2]OH+, [CH2–CH2–CH2]OH+, (CH3)2OC2H5+, [CH2–CH2–CH2–CH2]OH+, C2H5OH2+, (C2H5)2OH+, (C2H5)2OCH3+, [CH2–CH2–CH2–CH2–CH2]OH+, and (C2H5)3O+. The data are presented (in the Supporting Information) as seven-term NASA polynomials, to be used by chemical kineticists. Wherever available, estimates of the enthalpies of formation are compared to the literature.