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Ab initio and density functional theory study of structures and energies for dimethoxymethane as a model for the anomeric effect
Author(s) -
Kneisler John R.,
Allinger Norman L.
Publication year - 1996
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(199605)17:7<757::aid-jcc1>3.0.co;2-r
Subject(s) - dimethoxymethane , density functional theory , ab initio , chemistry , computational chemistry , anomeric effect , dihedral angle , bond length , ramachandran plot , molecular geometry , conformational isomerism , anomer , molecule , stereochemistry , hydrogen bond , organic chemistry , biochemistry , protein structure , catalysis
Ab initio molecular orbital theory and density functional theory calculations have been carried out on dimethoxymethane as a model for the anomeric effect. We optimized various conformations of dimethoxymethane using Gaussian 92 at the MP2/6‐311 + + G**, MP2/DZP + Diffuse, MP2/6‐31G**, and Becke3LYP/6‐31G** levels of theory. These methods were evaluated based on their performance in reproducing structures and energies of dimethoxymethane when compared to experiment. This study also examined the structure and energy of dimethoxymethane as a function of dihedral angles for examining the anomeric effect at the MP2/6‐31G** and Becke3LYP/6‐31G** levels of theory. These calculations are qualitatively consistent with the anomeric effect observations in carbohydrates and with earlier calculations. Quantitative comparisons with earlier results reveal that dimethoxymethane has lower total energies, smaller rotational barriers, and shorter bond lengths than was previously determined. The Becke3LYP calculations were also compared to the MP2 results. The density functional theory findings show that the minimum energy structures correspond well with experimental and MP2 data. The total and relative energies from molecular orbital theory and density functional theory vary to some extent. Contour plots of the relative energies of dimethoxymethane were evaluated and compared to a relative energy contour plot determined by MM3. The contour plots were similar, showing slightly larger changes in energies for the MP2 results than for the Becke3LYP results, which in turn were slightly larger than the MM3 results. Density functional theory calculations are an excellent alternative method of calculation due to increased speed and reliable accuracy of the density functional calculations. These results will serve as a benchmark for modelling the anomeric effect in carbohydrates. © 1996 John Wiley & Sons, Inc.