Structures and C–H bond energies of hydrogenated polycyclic aromatic hydrocarbons

May, Klaus; Unterreiner, Barbara V.; Dapprich, Stefan; Ahlrichs, Reinhart

doi:10.1039/b005597m

Cited by 17 publications

(18 citation statements)

References 13 publications

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“…In this work, we investigate the reaction of atomic hydrogen with a number of PAHs, complementing previous related studies 21,22,[24][25][26] which showed preference for addition at the edges of selected PAH molecules. The main aim of this study was to emphasize the importance of substrate relaxation ("geometrical") effects in determining a preference towards the edges.…”

Section: Introductionmentioning

confidence: 81%

“…We start by showing the preference for adsorption on the edge sites which was already noted by several authors 21,22,[24][25][26] . Fig.…”

Section: Resultsmentioning

confidence: 99%

“…For instance, hydrogenation is known to occurs much more easily on a zig-zag than on an armchair edge of large area graphene: May et al 25 , for instance, extrapolated DFT values computed on finite size graphenes towards the infinite size limit and obtained 2.86±0.15 eV for the zig-zag edge and 1.74±0.11 eV for the armchair one. This is consistent with the "rules" found here.…”

Section: Discussionmentioning

confidence: 99%

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A few simple rules governing hydrogenation of graphene dots

Bonfanti

Casolo

Tantardini

et al. 2011

The Journal of Chemical Physics

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We investigated binding of hydrogen atoms to small Polycyclic Aromatic Hydrocarbons (PAHs) -i.e. graphene dots with hydrogen-terminated edges -using density functional theory and correlated wavefunction techniques. We considered a number of PAHs with 3 to 7 hexagonal rings and computed binding energies for most of the symmetry unique sites, along with the minimum energy paths for significant cases. The chosen PAHs are small enough to not present radical character at their edges, yet show a clear preference for adsorption at the edge sites which can be attributed to electronic effects. We show how the results, as obtained at different level of theory, can be rationalized in detail with the help of few simple concepts derivable from a tight-binding model of the π electrons.

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Section: Introductionmentioning

confidence: 81%

“…We start by showing the preference for adsorption on the edge sites which was already noted by several authors 21,22,[24][25][26] . Fig.…”

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A few simple rules governing hydrogenation of graphene dots

Bonfanti

Casolo

Tantardini

et al. 2011

The Journal of Chemical Physics

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“…It is of value to try to validate the accuracy of the common density functional methods in these systems where other higher accuracy calculation methods are not available [1,2].…”

Section: Introductionmentioning

confidence: 99%

Enthalpy of formation and bond energies on unsaturated oxygenated hydrocarbons using G3MP2B3 calculation methods

Sebbar

Bozzelli

Bockhorn

2005

Int J of Chemical Kinetics

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Enthalpies of unsaturated oxygenated hydrocarbons and radicals corresponding to the loss of hydrogen atoms from the parent molecules are intermediates and decomposition products in the oxidation and combustion of aromatic and polyaromatic species. values. The deviation between G3MP2B3 and B3LYP methods is under ±0.5 kcal mol −1 for 9 species, 18 other species differs by less than ±1 kcal mol −1 , and 11 species differ by about 1.5 kcal mol −1 . Under them are 11 radicals derived from the above-oxygenated hydrocarbons that show good agreement between G3MP2B3 and B3LYP methods. G3 calculations have been performed to further validate enthalpy values, where a discrepancy of more than 2.5 kcal mol −1 exists between the G3MP3B3 and density functional results. Surprisingly the G3 calculations support the density functional calculations in these several nonagreement cases. C 2005 Wiley Periodicals, Inc. Int J Chem

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“…Peripheral C atoms are bonded to only two other C atoms. May et al (2000) and Rauls & Hornekaer (2008) have shown that due to lower energy barriers for hydrogen addition and considerably higher dissociation energies the formation of sp 3 centers is more likely to occur on outer C atoms. The inner part of a larger PAH remains aromatic as long as the periphery is not fully saturated.…”

Section: Hydrogenation Of Peripheral C Atomsmentioning

confidence: 99%

The Abundances of Hydrocarbon Functional Groups in the Interstellar Medium Inferred From Laboratory Spectra of Hydrogenated and Methylated Polycyclic Aromatic Hydrocarbons

Steglich

Jäger

Huisken

et al. 2013

ApJS

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Infrared (IR) absorption spectra of individual polycyclic aromatic hydrocarbons (PAHs) containing methyl (-CH 3 ), methylene ( CH 2 ), or diamond-like CH groups and IR spectra of mixtures of methylated and hydrogenated PAHs prepared by gas-phase condensation were measured at room temperature (as grains in pellets) and at low temperature (isolated in Ne matrices). In addition, the PAH blends were subjected to an in-depth molecular structure analysis by means of high-performance liquid chromatography, nuclear magnetic resonance spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Supported by calculations at the density functional theory level, the laboratory results were applied to analyze in detail the aliphatic absorption complex of the diffuse interstellar medium at 3.4 μm and to determine the abundances of hydrocarbon functional groups. Assuming that the PAHs are mainly locked in grains, aliphatic CH x groups (x = 1, 2, 3) would contribute approximately in equal quantities to the 3.4 μm feature (N CHx /N H ≈ 10 −5 -2 × 10 −5 ). The abundances, however, may be two to four times lower if a major contribution to the 3.4 μm feature comes from molecules in the gas phase. Aromatic CH groups seem to be almost absent from some lines of sight, but can be nearly as abundant as each of the aliphatic components in other directions (N CH /N H 2 × 10 −5 ; upper value for grains). Due to comparatively low binding energies, astronomical IR emission sources do not display such heavy excess hydrogenation. At best, especially in protoplanetary nebulae, CH 2 groups bound to aromatic molecules, i.e., excess hydrogens on the molecular periphery only, can survive the presence of a nearby star.

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Structures and C–H bond energies of hydrogenated polycyclic aromatic hydrocarbons

Cited by 17 publications

References 13 publications

A few simple rules governing hydrogenation of graphene dots

A few simple rules governing hydrogenation of graphene dots

Enthalpy of formation and bond energies on unsaturated oxygenated hydrocarbons using G3MP2B3 calculation methods

The Abundances of Hydrocarbon Functional Groups in the Interstellar Medium Inferred From Laboratory Spectra of Hydrogenated and Methylated Polycyclic Aromatic Hydrocarbons

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