Bond-Function Analysis of Rotational Barriers: Ethane

Sovers, O. J.; Kern, C. W.; Pitzer, Russell M.; Karplus, Martin

doi:10.1063/1.1670458

Cited by 171 publications

(72 citation statements)

References 26 publications

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“…Corrections for this electrostatic effect have been incorporated into some previous methods of barrier w x calculation 4,5,8,25,26 . Systematic calculation of the contribution of the bond dipole interaction can be carried out in the framework of natural bond orbital analysis, but is beyond the scope of the present work.…”

Section: Resultsmentioning

confidence: 99%

Natural steric analysis of internal rotation barriers

Badenhoop¹,

Weinhold²

1999

Int. J. Quant. Chem.

188

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ABSTRACT:We apply natural bond orbital NBO steric analysis introduced in a . previous article to obtain the steric exchange contribution to the internal rotation barriers Ž . of butane, ethane, and other related molecules CH NH , CH OH, NH OH . The expected exchange repulsion between the two methyl group C-H bonds within van der Waals contact in butane is shown to be the major contributor to the syn barrier and provides a method for calculating allowed ranges of torsional angles in macromolecules. However, the exchange-energy difference between the staggered and eclipsed forms predict a counterintuitive eclipsed minimum for ethane, methylamine, and methanol. We show that the full SCF barrier in such apolar molecules can be reasonably approximated as a sum of this steric term plus the hyperconjugative terms as previously evaluated.

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Section: Resultsmentioning

confidence: 99%

Natural steric analysis of internal rotation barriers

Badenhoop¹,

Weinhold²

1999

Int. J. Quant. Chem.

188

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“…But this can be greatly lessened by using doubly occupied MO-like localized orbitals as bond functions. 42 In this way, the VB wave function as shown in eq.…”

Section: Block-localized Wave Function Methodsmentioning

confidence: 99%

How resonance assists hydrogen bonding interactions: An energy decomposition analysis

Beck

2006

J Comput Chem

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Block-localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance-assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between delocalization and hydrogen-bonding interactions. We examined the dimers of formic acid, formamide, 4-pyrimidinone, 2-pyridinone, 2-hydroxpyridine, and 2-hydroxycyclopenta-2,4-dien-1-one. In addition, we studied the interactions in -diketone enols with a simplified model, namely the hydrogen bonds of 3-hydroxypropenal with both ethenol and formaldehyde. The intermolecular interaction energies, either with or without the involvement of resonance, were decomposed into the Hitler-London energy (DE HL ), polarization energy (DE pol ), charge transfer energy (DE CT ), and electron correlation energy (DE cor ) terms. This allows for the examination of the character of hydrogen bonds and the impact of conjugation on hydrogen bonding interactions. Although it has been proposed that resonance-assisted hydrogen bonds are accompanied with an increasing of covalency character, our analyses showed that the enhanced interactions mostly originate from the classical dipoledipole (i.e., electrostatic) attraction, as resonance redistributes the electron density and increases the dipole moments in monomers. The covalency of hydrogen bonds, however, changes very little. This disputes the belief that RAHB is primarily covalent in nature. Accordingly, we recommend the term ''resonance-assisted binding (RAB)'' instead of ''resonance-assisted hydrogen bonding (RHAB)'' to highlight the electrostatic, which is a long-range effect, rather than the electron transfer nature of the enhanced stabilization in RAHBs.

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“…EDA calculations were performed with two CH 3 neutral radicals as the monomers. Since the staggered and eclipsed forms are constructed from exactly the same CH 3 groups, their final energy difference can be understood from the CH 3 -CH 3 34 Calculations with ROMP2, UMP2, RO-B3LYP, and RO-BLYP methods lead to essentially the same conclusion, although the two MP2 methods give total interaction energies that are ϳ7 kcal/ mol stronger than those predicted with RO-CCSD and the two DFT methods ͑Table I͒. This is simply a fact that for CH 3 radical, which is an open shell system, MP2 predicts less amount of correlation energy than does CCSD, while for the CH 3 -CH 3 neutral closed shell molecule, MP2 and CCSD predict more similar correlation energies.…”

Section: B Ethane Internal Rotation Barriermentioning

confidence: 99%

Energy decomposition analysis of covalent bonds and intermolecular interactions

2009

The Journal of Chemical Physics

916

800

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An energy decomposition analysis method is implemented for the analysis of both covalent bonds and intermolecular interactions on the basis of single-determinant Hartree-Fock ͑HF͒ ͑restricted closed shell HF, restricted open shell HF, and unrestricted open shell HF͒ wavefunctions and their density functional theory analogs. For HF methods, the total interaction energy from a supermolecule calculation is decomposed into electrostatic, exchange, repulsion, and polarization terms. Dispersion energy is obtained from second-order Møller-Plesset perturbation theory and coupled-cluster methods such as CCSD and CCSD͑T͒. Similar to the HF methods, Kohn-Sham density functional interaction energy is decomposed into electrostatic, exchange, repulsion, polarization, and dispersion terms. Tests on various systems show that this algorithm is simple and robust. Insights are provided by the energy decomposition analysis into H 2 , methane C-H, and ethane C-C covalent bond formation, CH 3 CH 3 internal rotation barrier, water, ammonia, ammonium, and hydrogen fluoride hydrogen bonding, van der Waals interaction, DNA base pair formation, BH 3 NH 3 and BH 3 CO coordinate bond formation, Cu-ligand interactions, as well as LiF, LiCl, NaF, and NaCl ionic interactions.

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Bond-Function Analysis of Rotational Barriers: Ethane

Cited by 171 publications

References 26 publications

Natural steric analysis of internal rotation barriers

Natural steric analysis of internal rotation barriers

How resonance assists hydrogen bonding interactions: An energy decomposition analysis

Energy decomposition analysis of covalent bonds and intermolecular interactions

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