Accurate thermochemistry for larger molecules: Gaussian-2 theory with bond separation energies

Raghavachari, Krishnan; Stefanov, Boris B.; Curtiss, Larry A.

doi:10.1063/1.473659

Cited by 192 publications

(219 citation statements)

References 22 publications

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“…Absolute energies were obtained for the series of sulfenic acids and esters and radicals using the G2, G2(MP2), and G2(MP2,SVP) protocols. [23][24][25][26][27]33 The G2 energies and the optimized geometries are available in the Supporting Information. Spin contamination on all radicals not containing the vinyl group was quite modest (S 2 e 0.76).…”

Section: Resultsmentioning

confidence: 99%

Thermochemistry of Sulfenic Esters (RSOR‘): Not Just Another Pretty Peroxide

Gregory

Jenks

1998

J. Org. Chem.

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A computational study on the thermochemistry of several simple sulfenic acids (RSOH) and esters (RSOR′) is reported. The enthalpies of R-S, S-O, and O-R′ homolytic cleavage are calculated at the G2 level of theory and compared to related peroxides and disulfides. Less expensive B3LYP calculations were unsatisfactory. When R and R′ are both alkyl, the O-C bond is expected to be the weakest in the molecule; for CH 3 SOCH 3 , C-S, S-O, and O-C bond dissociation enthalpies of 67, 64, and 49 kcal/mol are predicted by G2. Compared to peroxides, sulfenic esters are predicted to have weaker O-C bonds and S-O bonds that are stronger than the analogous O-O bonds. The C-S bonds of sulfenic esters are predicted to be somewhat stronger than those of disulfides. A rationalization is given for the observation that radical stabilization is greater for RSO• than ROO• , RSS• , or ROS • .

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Section: Resultsmentioning

confidence: 99%

Thermochemistry of Sulfenic Esters (RSOR‘): Not Just Another Pretty Peroxide

Gregory

Jenks

1998

J. Org. Chem.

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“…The Gn methods have proven to be quite robust in this respect, described in detail within numerous successful applications and reviews. [6][7][8][9][10] Other composite methods have been created since the original formulation of the G1 method. Some of these, such as the complete basis set ͑CBS-n͒ model chemistries of Petersson and co-workers, [11][12][13][14] the focal point method of Allen and co-workers [15][16][17][18][19][20] and Császár et al, 21,22 the W1 and W2 methods of Parthiban and Martin 23 and Martin and de Oliveira, 24 and the High Accuracy Extrapolated ab initio Thermochemistry ͑HEAT͒ method of Stanton and co-workers, 25,26 attempt to approach the complete basis set ͑CBS͒/full-configuration interaction ͑FCI͒ limit of smaller systems, consistently obtaining accuracy better than within 0.5 kcal mol −1 of experimental data.…”

Section: Introductionmentioning

confidence: 99%

The correlation consistent composite approach (ccCA): An alternative to the Gaussian-n methods

DeYonker

Cundari

Wilson

2006

The Journal of Chemical Physics

307

327

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An alternative to the Gaussian-n ͑G1, G2, and G3͒ composite methods of computing molecular energies is proposed and is named the "correlation consistent composite approach" ͑ccCA, ccCA-CBS-1, ccCA-CBS-2͒. This approach uses the correlation consistent polarized valence ͑cc-pV XZ͒ basis sets. The G2-1 test set of 48 enthalpies of formation ͑⌬H f ͒, 38 adiabatic ionization potentials ͑IPs͒, 25 adiabatic electron affinities ͑EAs͒, and 8 adiabatic proton affinities ͑PAs͒ are computed using this approach, as well as the ⌬H f values of 30 more systems. Equilibrium molecular geometries and vibrational frequencies are obtained using B3LYP density functional theory. When applying the ccCA-CBS method with the cc-pVXZ series of basis sets augmented with diffuse functions, mean absolute deviations within the G2-1 test set compared to experiment are 1.33 kcal mol −1 for ⌬H f , 0.81 kcal mol −1 for IPs, 1.02 kcal mol −1 for EAs, and 1.51 kcal mol −1 for PAs, without including the "high-level correction" ͑HLC͒ contained in the original Gn methods. Whereas the HLC originated in the Gaussian-1 method as an isogyric correction, it evolved into a fitted parameter that minimized the error of the composite methods, eliminating its physical meaning. Recomputing the G1 and G3 enthalpies of formation without the HLC reveals a systematic trend where most ⌬H f values are significantly higher than experimental values. By extrapolating electronic energies to the complete basis set ͑CBS͒ limit and adding G3-like corrections for the core-valence and infinite-order electron correlation effects, ccCA-CBS-2 often underestimates the experimental ⌬H f , especially for larger systems. This is desired as inclusion of relativistic and atomic spin-orbit effects subsequently improves theoretical ⌬H f values to give a 0.81 kcal mol −1 mean absolute deviation with ccCA-CBS-2. The ccCA-CBS method is a viable "black box" method that can be used on systems with at least 10-15 heavy atoms.

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“…Raghavachari et al 34 have proposed to use a standard set of isodesmic reactions, the "bond separation reactions", 35 to derive the theoretical enthalpies of formation. This method has been detailed in previous studies.…”

Section: Resultsmentioning

confidence: 99%

The thermochemistry of alkanethiols and thioethers. Estimation of the enthalpies of formation of 1,3-dithiapropane and 1,3,5-trithiapentane

Notario¹,

Roux²

2005

Arkivoc

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We have carried out a study on the thermochemistry of alkanethiols and thioethers. Relationships between the enthalpies of formation of alkanes, alkanethiols, and thioethers are discussed with the purpose of deriving different group interconversion contributions that permit the estimation of unknown ∆ f H 0 m (g) values for alkanethiols and thioethers from known values of alkanes. We have also carried out a theoretical study at the G2(MP2), G2, and G3 levels, calculating the enthalpies of formation of two compounds, 1,3-dithiapropane and 1,3,5-trithiapentane, and comparing them with the values previously estimated.

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Accurate thermochemistry for larger molecules: Gaussian-2 theory with bond separation energies

Cited by 192 publications

References 22 publications

Thermochemistry of Sulfenic Esters (RSOR‘): Not Just Another Pretty Peroxide

Thermochemistry of Sulfenic Esters (RSOR‘): Not Just Another Pretty Peroxide

The correlation consistent composite approach (ccCA): An alternative to the Gaussian-n methods

The thermochemistry of alkanethiols and thioethers. Estimation of the enthalpies of formation of 1,3-dithiapropane and 1,3,5-trithiapentane

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