Ab initio calculations have been carried out on s-trans-Nvinylmethyleneammonium, pyridinium, and related compounds to obtain rotational barriers, structures, and vibrational frequencies. The restricted Hartree-Fock (RHF) level of theory with 6-31G\*\* basis set was used for these calculations. In ad
Ab initio and molecular mechanics (MM2 and MM3) calculations of nonconjugated positively charged nitrogen-containing compounds
β Scribed by Georgia B. McGaughey; Eugene L. Stewart; J. Phillip Bowen
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 711 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0192-8651
No coin nor oath required. For personal study only.
β¦ Synopsis
Abstract
Highβlevel ab initio calculations have been performed on NβmethylβNβmethyleneammonium and related compounds to obtain accurate rotational barriers, structures, and vibrational frequencies. The 6β31G** basis set has been utilized at the HartreeβFock level of theory for these calculations because little experimental data are available. The MM2(91) and MM3(94) force fields have been parameterized to include these nonconjugated charged nitrogenβcontaining compounds. Molecular mechanics geometries and vibrational frequencies compare well with the ab initio results. Β© 1995 John Wiley & Sons, Inc.
π SIMILAR VOLUMES
The boronic acid functional group has been incorporated into various biologically important compounds. In order to study this class of compounds better with molecular mechanics, five alkyl-and arylboronic acids were calculated using ab initio methods (Spartan) at the RHF/6-31G \* level. MM3 force fi
Ab initio calculations at both the Hartree-Fock and M~ller-Plesset (MP2) levels of theory utilizing various basis sets were carried out on propargyl alcohol and its derivatives. The results of these calculations were used in conjunction with available experimental data in the formulation of an MM3 f
The geometries and vibrational frequencies of 11 training molecules containing the ammonium ion moiety were calculated at the MP2r6-31qG U level of theory. Various torsional energy profiles were also calculated using this basis set. From those ab initio calculations, a molecular mechanics Ε½ . MM3 fo
Simple and very efficient formulas are presented for four-body ## Ε½ . out-of-plane bend used in MM2 and MM3 force fields and improper torsion Ε½ . used in the MM4 force field internal coordinates and their first and second derivatives. The use of a small set of bend and stretch intermediates allow
β‘ Ε½ . β¬G 298 K values were in good agreement with experimental values published recently. In addition, we also performed MM3 calculations on Si H and 2 6 Si Me . MM3 calculated rotational barriers and thermodynamic properties were 2 6 compared with high level ab initio results. Based on this compari