Accurate Calculations of Bond Dissociation Enthalpies with Density Functional Methods

Yao, Xiaoqian; Hou, Xinjuan; Jiao, Haijun; Xiang, Huimin; Li, Yongwang

doi:10.1021/jp0361125

Cited by 110 publications

(85 citation statements)

References 51 publications

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“…In general it appears when a first-row atom or group X (X = B, C, N) is successively alkylated. Gilbert [3] found increasing errors of the B3LYP functional (up to 20 kcal mol À1 ) for the dissociation reaction (1) when R = H is replaced by CH 3 .Similar results were reported later [4,5] for the CÀC bond dissociation reaction (2) and [2+2] cycloadditions and CH 2 -[*] Prof. …”

supporting

confidence: 69%

Seemingly Simple Stereoelectronic Effects in Alkane Isomers and the Implications for Kohn–Sham Density Functional Theory

2006

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The concept of stereoelectronic (SE) effects is widely applied especially in organic chemistry.[1] Substituents are typically described as electron-density-donating or -withdrawing or responsible for sterically interacting with, for example, reagents. The rational application of SE design rules is of utmost importance in synthetic chemistry where target structures are often kinetically or thermodynamically favored. Important SE effects can be introduced by alkylation (methylation in the following discussion for simplicity) of strategic positions in a molecule. The resulting energetic changes can be qualitatively separated into so-called electronic (bonding) and nonbonding (through-space, i.e., attractive van der Waals (vdW) and electrostatic, and repulsive Pauli) interactions. While a meaningful definition and separation of these individual terms is quite difficult at a rigorous quantum mechanical level, it is generally believed that modern quantum chemical methods are at least able to describe the overall energetic effects quantitatively. It is shown in this Communication that this does not hold for the widely used Kohn-Sham density functional theory (DFT) [2] with all state-of-the-art density functionals; this approach does not provide even a qualitatively correct picture for an important class of chemical problems.The problem has become evident in recent years since larger molecular systems have been studied more routinely. In general it appears when a first-row atom or group X (X = B, C, N) is successively alkylated. Gilbert [3] found increasing errors of the B3LYP functional (up to 20 kcal mol À1 ) for the dissociation reaction (1) when R = H is replaced by CH 3 .Similar results were reported later [4,5] for the CÀC bond dissociation reaction (2) and [2+2] cycloadditions and CH 2 -[*] Prof.

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supporting

confidence: 69%

Seemingly Simple Stereoelectronic Effects in Alkane Isomers and the Implications for Kohn–Sham Density Functional Theory

2006

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“…[14,17,30,[60][61][62][63][64][65][66][67][68][69][70][71][72][73][74] Check and Gilberts analysis of homolytic CÀC bond breaking energies of methyl-substituted ethane show B3LYP to have increasing errors as the number of methyl group substitutions is increased. [60] We have recently tested a large number of density functionals by computing the Pople bond separation reaction energies of n-alkanes (propane through decane) and found that all functionals systematically underestimate the energy of these reactions.…”

Section: Computational Modelsmentioning

confidence: 99%

The Concept of Protobranching and Its Many Paradigm Shifting Implications for Energy Evaluations

Wodrich

Wannere

et al. 2007

Chemistry A European J

189

203

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Branched alkanes like isobutane and neopentane are more stable than their straight chain isomers, n-butane and n-pentane (by 2 and 5 kcal mol(-1), respectively). Electron correlation is largely responsible. Branched alkanes have a greater number of net attractive 1,3-alkyl-alkyl group interactions, there are three such stabilizing 1,3 "protobranching" dispositions in isobutane, but only two in n-butane. Neopentane has six protobranches but n-pentane only three. Propane has one protobranch and is stabilized appreciably, by 2.8 kcal mol(-1), relative to methane and ethane. This value per protobranch also applies to the n-alkanes and cyclohexane. Consequently, energy evaluations employing alkane reference standards, for example, of small ring strain and stabilizations due to conjugation, hyperconjugation, and aromaticity, should be corrected for protobranching, for example, by employing Pople's isodesmic bond separation reaction method. This reduces the ring strain of cyclopropane to 19.2 from the conventional 27.7 kcal mol(-1), while the stabilization energies of alkenes and alkynes due to hyperconjugation (5.5 and 7.7 kcal mol(-1) for propene and propyne) and conjugation (14.8 and 27.1 kcal mol(-1) for butadiene and butadiyne) are considerably larger than the traditional estimates. Widely diverging literature evaluations of benzene resonance energy all give approximately 65 kcal mol(-1) after adjusting for conjugation, hyperconjugation, and protobranching "contaminations." The BLW (block localized wavefunction) method, which localizes pi bonds and precludes their interactions, largely confirms these stabilization estimates for hyperconjugation, conjugation, and aromaticity. Protobranching is seriously underestimated by theoretical computations at the HF and most DFT levels, which do not account for electron correlation satisfactorily. Such levels give bond separation energies, which can differ greatly from experimental values.

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“…Similar conclusions were found by Yao and co-workers, who explored the accuracy obtained by a variety of hybrid functionals and coupled cluster treatments for calculating the BDEs. [37] The work of Feng et al is also worth mentioning since it concerns an assessment of BDEs using both composite ab initio methods and various DFT methods on a very complete dataset. Golden and co-workers further confirmed that the commonly used B3LYP method is insufficient for an accurate evaluation of BDEs and suggested other hybrid methods such as the KMLYP method, that yield rootmean-square (RMS) deviations that are close to the experimental error bars.…”

Section: Phenanthrene Dibenzoa C H T U N G T R E N N U N G [Cg]phenmentioning

confidence: 99%

Hydrocarbon Bond Dissociation Enthalpies: From Substituted Aromatics to Large Polyaromatics

2006

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Hydrocarbon-bond dissociation enthalpies (BDE) at 298 K are calculated for a set of hydrocarbons. An efficient method for calculating the BDE values is derived on the basis of a comparative study with experimental data. The methods considered are based on density functional theory (DFT) including the B3LYP, MPW1PW91, B3P86, B3PW91, MPW1P86, KMLYP, MPW1K and BMK functionals. The commonly known sequence for radical stability is quantified on the basis of BDE values. The recommended procedure is extrapolated to substituted aromatics and large polyaromatic hydrocarbons (PAHs) to obtain insight into the factors that govern the stability of the radicals. Furthermore it is shown that BDEs are also good reactivity descriptors for subsequent additions involving the formed radicals. Linear correlations, similar to classical Evans-Polanyi-Semenov plots, between the BDE and the reaction barriers for addition reactions with ethene, ethyne, propene, propyne and butadiene are found, as the exothermicity is primarily determined by the stability of the originating reactant radical.

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Accurate Calculations of Bond Dissociation Enthalpies with Density Functional Methods

Cited by 110 publications

References 51 publications

Seemingly Simple Stereoelectronic Effects in Alkane Isomers and the Implications for Kohn–Sham Density Functional Theory

Seemingly Simple Stereoelectronic Effects in Alkane Isomers and the Implications for Kohn–Sham Density Functional Theory

The Concept of Protobranching and Its Many Paradigm Shifting Implications for Energy Evaluations

Hydrocarbon Bond Dissociation Enthalpies: From Substituted Aromatics to Large Polyaromatics

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