Steric and electronic substituent effects on the carbon-carbon bond

Rüchardt, Christoph; Beckhaus, Hans‐Dieter

doi:10.1007/3-540-15810-3_1

Cited by 108 publications

(22 citation statements)

References 68 publications

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“…This explains why the results shown in Table S2 are an indication that by adding moderate corrections, one can obtain excellent agreement between model and experimental results. It is interesting to note that the "correction" we introduced for 2,2-dimethylpentane is 6.8 kJ/mol, whereas Rüchardt and Beckhaus (case 9d, Table 2 in reference [17]) have calculated the strain energy is 6.7 kJ/mol, an agreement suggesting that our corrections are the strain enthalpies assigned by Rüchardt and Beckhaus.…”

Section: Dimethyl Alkanessupporting

confidence: 53%

“…The dimethylalkanes are still relatively unstrained in the sense as discussed by Rüchardt and Beckhaus [16,17]. This explains why the results shown in Table S2 are an indication that by adding moderate corrections, one can obtain excellent agreement between model and experimental results.…”

Section: Dimethyl Alkanesmentioning

confidence: 69%

“…During the investigations that led to the present paper, and while having studied the higher substituted alkanes, di-, tri-, and tetra-alkylalkanes, we found that also for the monomethylalkanes geminal effects play a role, even though limited regarding the magnitude. When one studies the optimized molecular structures for the monomethylalkanes after energy minimization employing DFT calculations, one does observe changes in CCC bond angles along the main alkyl chain, making the entire chain a little bent (such as described by Rüchardt and Beckhaus [16,17]). In the work of [1], we had the formulas…”

Section: Mono-methyl Alkanesmentioning

confidence: 99%

“…This, however, cannot be a surprise when studying the chemical literature and, more specifically, geminal (the relationship between two atoms or functional groups that are attached to the same atom) effects and steric effects on the entire molecular conformational structure. In this context, two papers by Rüchardt and Beckhaus [16,17] and references therein to their earlier published experimental data are very worthwhile reading in this context. They also referenced back to them in this context the pioneering work of Karl Ziegler from the 1940s on factors determining C-C bond strengths.…”

Section: Alkyl-substituted Alkanes: Introductionmentioning

confidence: 98%

“…In more detail, the steric effects of two neighboring methyl substituents, i.e., as in -C-C(CH 3 )-C(CH 3 )-C-C-, may initially be regarded as just a van der Waals interaction between such groups. However, what is disregarded and specifically emphasized by Rüchardt and Beckhaus [16,17] is the effect that the presence of the substituents has on the conformational structure of the backbone alkane. Whereas an unsubstituted alkane can be drawn as an all-trans C-C chain, the substituents induce changes in C-C bond lengths, valence (CCC), and torsional (CCCC) angles, the extent depending on the degree, type, and location of the substitutions.…”

Section: Alkyl-substituted Alkanes: Introductionmentioning

confidence: 99%

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Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part II

Meier¹

2021

AppliedChem

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Group contribution (GC) methods to predict thermochemical properties are eminently important to process design. We present a group contribution parametrization for the heat of formation of organic molecules exhibiting chemical accuracy, maximum 1 kcal/mol (4.2 kJ/mol) difference between experiment and model values while minimizing the number of parameters avoiding overfitting and therewith avoiding reduced predictability. Compared to the contemporary literature, this was successfully achieved by employing available literature high-quality and consistent experimental data, optimizing parameters group by group, and introducing additional parameters when chemical understanding was obtained supporting these. A further important result is the observation that the applicability of the group contribution approach breaks down with increasing substitution levels, i.e., more heavily alkyl-substituted molecules, the reason being a serious influence of substitution on the conformation of the flexible part of the entire molecule within particular valence angles and torsional angles affected, which cannot be accounted for by additional GC parameters with fixed numerical values.

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Section: Dimethyl Alkanessupporting

confidence: 53%

Section: Dimethyl Alkanesmentioning

confidence: 69%

Section: Mono-methyl Alkanesmentioning

confidence: 99%

Section: Alkyl-substituted Alkanes: Introductionmentioning

confidence: 98%

Section: Alkyl-substituted Alkanes: Introductionmentioning

confidence: 99%

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Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part II

Meier¹

2021

AppliedChem

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An Electronegativity Model for Polar Ground-State Effects on Bond Dissociation Energies

Nau¹

1997

J. Phys. Org. Chem.

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Homolytic bond dissociation energies are a composite of the radical stabilization energies (RSE) of the product radicals and the polar ground-state stabilization energies (PSE) of the reactant molecules. Substituent effects on the PSE are rationalized in terms of changes in the difference of group electronegativities. Thus, the PSE is composed of a bond polarity term, which measures the contribution due to the change in the electronegativity difference between the atoms in the bond, which is broken, and a polar relaxation term, which accounts for the substituent-dependent group electronegativity changes in the remaining bonds. A semi-quantitative model based on Pauling's bonding theory is suitable to assess the direction and relative magnitude of such effects. For the cleavage of benzylic and related bonds, the polar relaxation energy can be neglected (one-bond approximation) to allow the use of correlation analyses and substituent parameters for the interpretation of aryl substituent effects on the PSE. Accordingly, the plots of the PSEs versus substituent parameters should be linear, curved or parabolic depending on the electronegativity difference of the atoms in the bond being broken (⌬EN); moreover, the slopes ( values) should increase linearly with ⌬EN. The predicted dependences of the PSEs on aryl substituents are compared with known experimental results and with the data obtained from semiempirical calculations.

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Structural dependence of heterolytic bond dissociation energy of carbon–carbon σ bonds in hydrocarbons

Kitagawa

Takeuchi

1998

J. Phys. Org. Chem.

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The coordination of a resonance-stabilized hydrocarbon cation and anion yielded a series of unprecedented hydrocarbons, which are susceptible to thermal heterolytic cleavage of carbon-carbon s bonds in polar media, generating the original ions under reversible conditions. When the component ions were sufficiently stabilized, some ion pairs were even isolated as solids, thus providing the first examples of hydrocarbon salts. The direct observation of the heterolysis by means of spectroscopy permitted reliable thermodynamic treatments of the observed degree of ionic dissociation. Correlation of the free energy of heterolysis with solvent dielectric constants and parameters of ion stabilities such as pK HA , pK R and redox potentials revealed the importance of the thermodynamic stabilities of ions, the degree of solvation and steric congestion in the starting molecule as major controlling factors in the heterolysis.

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Steric and electronic substituent effects on the carbon-carbon bond

Cited by 108 publications

References 68 publications

Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part II

Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part II

An Electronegativity Model for Polar Ground-State Effects on Bond Dissociation Energies

Structural dependence of heterolytic bond dissociation energy of carbon–carbon σ bonds in hydrocarbons

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