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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method

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Origin of anomeric effect: a density functional steric analysis.

Ying Huang¹, Ai-Guo Zhong, Qinsong Yang

¹School of Pharmacy, Hunan University of Chinese Medicine, Changsha, Hunan, China.

The Journal of Chemical Physics

|March 3, 2011

Summary

This summary is machine-generated.

The anomeric effect, a chemical phenomenon, is not always true and can be violated. A novel explanation reveals it

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Spatial Separation of Molecular Conformers and Clusters

Spatial Separation of Molecular Conformers and Clusters

Published on: January 9, 2014

Area of Science:

Organic Chemistry
Computational Chemistry

Background:

The anomeric effect describes the preference for axial over equatorial substituents in cyclic systems.
Traditional explanations involve dipole repulsion or hyperconjugation.
A stereoelectronic origin is widely accepted but lacks a definitive explanation.

Purpose of the Study:

To provide a novel, two-component explanation for the anomeric effect.
To investigate the validity and underlying factors of the anomeric effect using computational methods.
To explore the energy components contributing to axial-equatorial conformational preferences.

Main Methods:

Employed density functional steric analysis on α-D-glucopyranose.
Systematically explored conformational space, generating 32 isomers and 80 axial-equatorial pairs.
Analyzed energy differences and correlations between various energy components (exchange-correlation, electrostatic, steric).

Main Results:

The anomeric effect is statistically valid but not universally true and can be violated.
Exchange-correlation, electrostatic, and steric energy components correlate with energy differences.
Total dipole moment change is a better indicator than hyperconjugation, but not fully explanatory.
A novel two-component explanation based on steric hindrance and classical electrostatic interactions is proposed.

Conclusions:

The axial-equatorial energy difference, including the anomeric effect, is governed by steric and electrostatic interactions.
These two factors work synchronously to dictate conformational preferences.
An alternative explanation involving exchange-correlation and electrostatic interactions was also derived.