Theoretical investigations of the nature of intramolecular interactions

Smits, Guido F.; Krol, Maarten; Hart, W.J. van der; Altona, C.

doi:10.1080/00268978600102021

Cited by 19 publications

(17 citation statements)

References 14 publications

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“…The NOLMO framework offers a good perspective for the extension of such a n analysis to larger molecules. 17 The method followed in the present investigation to study the anomeric effect on a theoretical level is to perform geometry optimizations on small model compounds and to calculate the energy differences between various conformers.12* ''…”

Section: Introductionmentioning

confidence: 99%

The anomeric effect: Ab‐initio studies on molecules of the type XCH₂OCH₃

Krol¹,

Juige²,

Altona³

1990

J Comput Chem

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The anomeric effect of the functional groups X = C s N , CECH, COOH, COO-, 0-CH3, NH2, and NH: has been studied with ab initio techniques. Geometry effects upon rotation around the central C-0 bond in X-CH2- have been compared in the various compounds. The energy differences between the conformers with a gauche and trans ( X -C -0 -C) arrangement were calculated at the 6-31G* level in the fully optimized 4-21G geometries. Energy differences calculated at the 4-21G level appeared not to be reliable, especially for the groups X that contain non-sp3 hybridized atoms. The 6-31G* energy differences indicate a normal anomeric effect for X = COO-, 0-CH3, and NH,(g') (ca. 13 kJ/mol) and a small anomeric effect for X = COOH, CEN, and C=CH (ca. 6 kJ/mol). For X = NH2(t) and NH: a reverse anomeric effect occurs. These observations are in line with experimental results and evidence is given for a competition among various stereoelectronic interactions that occur a t the same anomeric center. Geometry variations can be understood in terms of simple rules associated with anomeric orbital interactions. Trends followed when the group X is varied cannot be related in a straightforward way to the energy differences between the trans and the gauche forms in these compounds. Only the variation in the gauche torsion angle X-C -0 -C follows roughly the same trend.

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Section: Introductionmentioning

confidence: 99%

The anomeric effect: Ab‐initio studies on molecules of the type XCH₂OCH₃

Krol¹,

Juige²,

Altona³

1990

J Comput Chem

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“…In order to roughly match this interaction with V, a charge product of 0.083 e2 had to be assumed. This corresponds to an atomic charge of I .29 I e on the hydrogen, which is considerably higher than commonly used value^.^,'^ A comparison of the Fourier expansion coefficients of V, and the Coulombic potential (Table I) 19 There is accumulating evidence that these parameters have a strong coordinate dependence," and that, in particular, the derivatives of the atomic charges with respect to the internal coordinates (the "charge fluxes") can be comparable in size or even larger than the atomic charges themselves. When these fluxes are included in the coupling derivatives the local picture is, to some extent, lost, since the atomic parameters now depend on the coordinates of all other atoms.…”

Section: It Is Evident Frommentioning

confidence: 99%

A novel decomposition of torsional potentials into pairwise interactions: A study of energy second derivatives

Dinur¹,

Hagler²

1990

J Comput Chem

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A general method of analyzing intramolecular torsional potentials in terms of energy second derivatives that couple the rotating atoms is presented. The method offers a rigorous decomposition of the total torsional potential into pairwise (dihedral) interactions and enables one to derive nonbonded torsional interactions between 1-4 atoms as well as between more distant atoms and sites. The method is demonstrated on ethane, propane and acetaldehyde. It is shown that the 1-4 H . . . H dihedral potentials in ethane and propane are very similar, thereby supporting the notion of transferable force field potential functions. However, the dihedral potentials that are obtained differ from 1-4 potentials that are used in current force fields. Intramolecular three body effects are clearly seen in this method and are found to be relatively large for the dihedral interactions, although in the one case studied (propane) the overall effect on the methyl-methyl interaction is negligible due to cancellation of terms. The analysis explicitly shows that the barrier in acetaldehyde is due mainly to the dihedral H . . . H interaction.

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“…The interference density, which is the charge redistribution when overlap between the NOLMOs is admitted, turns out to be of vital importance in the analysis of small energy differences. In particular, the energy effects associated with geminalt interference interactions prove to be important [20][21][22]. This can be understood if one realizes that the overlap of two geminal NOLMOs usually exceeds the overlap of, for example, two vicinal NOLMOs.…”

Section: Introductionmentioning

confidence: 98%

“…However, in the calculation of small energy differences the quasi-classical energy gives erroneous results [19][20][21][22]. Thus overlap between NOLMOs can by no means be neglected.…”

Section: Introductionmentioning

confidence: 99%

“…In our laboratory the construction of non-orthogonal strictly localized molecular orbitals (NOLMOs) [18,19] was combined with an energy decomposition scheme [19,20], which resulted in a thorough analysis of barriers of internal rotation [20,21] and the anomeric effect [22]. Although the details of the method used can be found in previous publications, a brief summary will be given here.…”

Section: Introductionmentioning

confidence: 99%

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