scispace - formally typeset
Search or ask a question
Topic

Conformational isomerism

About: Conformational isomerism is a research topic. Over the lifetime, 11563 publications have been published within this topic receiving 199312 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: The origin of the internal rotation barrier between the eclipsed and staggered conformers of ethane and n-butane is systematically investigated and suggests that the new energy partition scheme provides insights from a different perspective of internal rotation barriers.
Abstract: On the basis of an alternative energy partition scheme where density-based quantification of the steric effect was proposed [Liu, S. B. J. Chem. Phys. 2007, 126, 244103], the origin of the internal rotation barrier between the eclipsed and staggered conformers of ethane and n-butane is systematically investigated in this work. Within the new scheme, the total electronic energy is decomposed into three independent components, steric, electrostatic, and fermionic quantum. The steric energy defined in this way is repulsive, exclusive, and extensive and intrinsically linked to Bader's atoms in molecules approach. Two kinds of differences, adiabatic (with optimal structure) and vertical (with fixed geometry), are considered for the molecules in this work. We find that in the adiabatic case the eclipsed conformer possesses a larger steric repulsion than the staggered conformer for both molecules, but in the vertical cases the staggered conformer retains a larger steric repulsion. For ethane, a linear relationship between the total energy difference and the fermionic quantum energy difference is discovered. This linear relationship, however, does not hold for n-butane, whose behaviors in energy component differences are found to be more complicated. The impact of basis set and density functional choices on energy components from the new energy partition scheme has been investigated, as has its comparison with another definition of the steric effect in the literature in terms of the natural bond orbital analysis through the Pauli Exclusion Principle. In addition, profiles of conceptual density functional theory reactivity indices as a function of dihedral angle changes have been examined. Put together, these results suggest that the new energy partition scheme provides insights from a different perspective of internal rotation barriers.

86 citations

Journal ArticleDOI
01 Jan 2002-Polymer
TL;DR: In this paper, the authors compare the conformational partition functions of poly(ethylene terephthalate) and poly(methylene 2,6-naphthalate) polyesters.

85 citations

Journal ArticleDOI
TL;DR: Introduction of an electron-withdrawing group on the aromatic ring of N-methylacetanilide decreased the ratio of the cis conformer, and the ratio correlates well with the Hammett sigma values of the substituents.

85 citations

Journal ArticleDOI
TL;DR: The conformational preference of calix[4]pyrrole and its fluoride and chloride anion-binding properties have been investigated by density functional theory calculations and the strength of N-H- - -anion hydrogen bonds in the various structures subject to study were estimated on the basis of the calculated anions-binding energies and the predicted structural deformation energies.
Abstract: The conformational preference of calix[4]pyrrole and its fluoride and chloride anion-binding properties have been investigated by density functional theory calculations. Geometries were optimized by the BLYP/3-21G and BLYP/6-31G* methods, and energies were evaluated with the BLYP/6-31+G** method. To model the effect of medium, the SCIPCM solvent model was also employed. Four typical conformations of the parent substituent-free calix[4]pyrrole were studied. Both in the gas phase and in CH2Cl2 solution, the stability sequence is predicted to be 1,3-alternate > partial cone > 1,2-alternate > cone. The cone conformation is predicted to be about 16.0 and 11.4 kcal/mol less stable in the gas phase and CH2Cl2 solution, respectively. This is mainly due to electrostatic repulsions arising from the all-syn pyrrole/pyrrole/pyrrole/pyrrole arrangement present in this conformer. The existence of possible 1:1 and 1:2 anion-binding modes were explored in the case of fluoride anion, and the factors favoring the 1:1 bindi...

85 citations

Journal ArticleDOI
TL;DR: In this article, two new thermally irreversible photochromic (R)-binaphthol-condensed indolylfulgides (with a 1,2-dimethyl-3-indolyl)-2-methylpropylidene group, 6 and 7, respectively) were synthesized.
Abstract: Two new thermally irreversible photochromic (R)-binaphthol-condensed indolylfulgides (with a 1-(1,2-dimethyl-3-indolyl)-2-methylpropylidene group and with a 1-(1,2-dimethyl-3-indolyl)butylidene group, 6 and 7, respectively) were synthesized. Because of rapid thermal equilibration between the conformational isomers of 7E at room temperature, photocyclization of a substantial portion of 7E occurred through (P)-7Eα to give (9aS)-7C selectively. On the other hand, as thermal equilibration requires a long time for 6E at room temperature, its photochromic interconversion occurs only between (P)-6Eα and (9aS)-6C, and the photocyclization-inert 6E remained unchanged. The thermal stability and fatigue resistivity toward the iterative photochromic interconversion of 7 have been proved to be excellent among the fulgide derivatives. The photochromic reactions were accompanied by large changes of specific rotation values. The X-ray crystallographic analysis of a visible-light-sensitive colored form, (9aS)-6C, was carr...

85 citations


Network Information
Related Topics (5)
Molecule
52.4K papers, 1.2M citations
93% related
Hydrogen bond
57.7K papers, 1.3M citations
92% related
Ab initio
57.3K papers, 1.6M citations
91% related
Nuclear magnetic resonance spectroscopy
42.6K papers, 1M citations
91% related
Ligand
67.7K papers, 1.3M citations
90% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023303
2022618
2021217
2020219
2019228
2018268