Journal ArticleDOI
MNDO study of conformational properties of cyclic sulfur diimides
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TLDR
In this article, semi-empirical SCF MO calculations are used to investigate the conformational properties of five-to eight-membered ring sulfur diimides. But the energy barrier for interconversion of C 2 and C s conformations is only 7.5 kJ mol −1.Abstract:
MNDO semiempirical SCF MO calculations are used to investigate the conformational properties of five- to eight-membered ring sulfur diimides ( 1–4 ). Dimethylene sulfur diimide ( 1 ) is planar with C 2 v symmetry. The plane symmetrical puckered conformation of trimethylene sulfur diimide ( 2 ) is calculated to be only 6.4 kJ mol −1 more stable than the planar C 2 v transition-state geometry. Tetramethylene sulfur diimide ( 3 ) has two energy-minimum conformations with the envelope ( C 2 ) form, being 2.5 kJ mol −1 more stable than the half-chair ( C s ) geometry. The calculated energy barrier for interconversion of C 2 and C s conformations is only 7.5 kJ mol −1 . Two energy-minimum conformations with similar energies were found for pentamethylene sulfur diimide ( 4 ), separated by a relatively high (29.6 kJ mol −1 ) energy barrier.read more
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Book ChapterDOI
Conformations of 1,2,4,6-Tetrathiepane
TL;DR: Ab initio calculations at HF/6-31+G*//HF/ 6-31-31 +G* and B3LYP/6.3-3-4-3+3-2-2+3 level of theory for geometry optimization and MP2/6,31+ G*// HF/5,3-5,2-3* level for a single point total energy calculation are reported for 1,2,4,6-tetrathie
Journal ArticleDOI
An Ab Initio Study of Conformational Energies in Dioxo-, Trioxo-, and Tetroxo-Dithianes
TL;DR: In this article, Hartree-Fock calculations at the HF/6-31G* level of theory for geometry optimization are reported for the important energy-minimum conformations of 1, 1-dioxo-thiane (2), 1,1dioxoxo-1,2-dithiane (3), 1 1,dioxioxo -1,3-ditieny (4), 1.1-Dioxo--1,4-dittieny(5), 1
Journal ArticleDOI
Conformational Energies in Organic Six-Membered Cyclic Sulfoxides
TL;DR: In this article, Hartree-Fock calculations at the HF/6−31 G* level of theory for geometry optimization and the MP2/6 −31 G * and B3LYP/6-311G* levels for a single point total energy calculation are reported for the important energy-minimum conformations of 1-oxo-thiane (1), 1, oxo-1,2-dithiane (2), 1oxo -1,3-ditiane (3, 1,oxo)-1,4-dittiane
Book ChapterDOI
Seven-membered Rings with Three Heteroatoms 1,2,3
A. Kiselyov,A. Khvat +1 more
TL;DR: This chapter deals with the seven-membered heterocyclic rings featuring three heteroatoms at positions 1, 2, and 3 of the ring and includes synthetic methodologies, reactivity, and theoretical studies of the title scaffolds.
Book ChapterDOI
Eight-membered Rings with Three Heteroatoms
TL;DR: In this article, structural and synthetic aspects of eight-membered heterocycles with three heteroatoms, triheterocines, are surveyed in conjunction with experimental spectroscopic data.
References
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Journal ArticleDOI
Ground States of Molecules. 38. The MNDO Method. Approximations and Parameters
Michael J. S. Dewar,Walter Thiel +1 more
Journal ArticleDOI
MOPAC: A semiempirical molecular orbital program
TL;DR: This work focuses on the calculations of vibrational spectra, thermodynamic quantities, isotopic substitution effects, and force constants in a fully integrated program for the study of chemical reactions involving molecules, ions, and linear polymers using MOPAC.
Journal ArticleDOI
Ground States of Molecules. 39. MNDO Results for Molecules Containing Hydrogen, Carbon, Nitrogen, and Oxygen
Michael J. S. Dewar,Walter Thiel +1 more
Journal ArticleDOI
Conformations and Strain Energy of Cyclopentane and its Derivatives
Kenneth S. Pitzer,Wilm E. Donath +1 more
Journal ArticleDOI
Location of transition states in reaction mechanisms
TL;DR: In this article, a general method for the location of transition states in reaction mechanisms is described, once reactants and products are characterised, and no assumptions as to the geometry of the transition state or of the mechanism are necessary.