Hyperconjugation not steric repulsion leads to the staggered structure of ethane

  title={Hyperconjugation not steric repulsion leads to the staggered structure of ethane},
  author={Vojislava Pophristic and Lionel Goodman},
Many molecules can rotate internally around one or more of their bonds so that during a full 360° rotation, they will change between unstable and relatively stable conformations. Ethane is the textbook example of a molecule exhibiting such behaviour: as one of its two methyl (CH3) groups rotates once around the central carbon–carbon bond, the molecule will alternate three times between an unstable eclipsed conformation and the preferred staggered conformation. This structural preference is… Expand
Dissecting the hindered rotation of ethane.
This work has shown that a zerothorder unperturbed system formed by two non-orthogonal sets cannot be put in correspondence with a Hermitian Hamiltonian, raising doubts about any physical argument obtained from a perturbative approach using such a model. Expand
Hyperconjugative interactions in vinylic systems: the problem of the barrier to methyl rotation in acetone
Abstract The origin of the barrier to methyl rotation in acetone has been studied through natural bond orbital theory. The analysis is divided in two parts, one involving the stability of bonds andExpand
Through space hyperconjugation in half-cage alcohols
Abstract Previous theoretical studies indicate that hyperconjugation and through-space interactions of a steric or electronic nature are mainly responsible for conformational effects in half-cageExpand
Severe Energy Costs of Double Steric Interactions: Towards a Molecular Clamp
The factors determining the ease of rotation about carbon-carbon single bonds connecting two internally rigid fragments such as phenyl, indenyl, anthracenyl and triptycyl are analysed. The internalExpand
On the origin of internal rotation in ammonia borane
The barrier to internal rotation in ammonia borane can be understood predominantly in a ‘classical’ way, as originating from the steric repulsion contributions (of the kinetic origin) that act solely between N–H and B–H bonds. Expand
Elucidation of the Forces Governing the Stereochemistry of Biphenyl
Biphenyl prefers a twisted conformation rather than a planar or perpendicular structure. Although conjugation (stabilization) and steric repulsion (destabilization) coexist in the planar structure,Expand
Turn: Weak Interactions and Rotational Barriers in Molecules-Insights from Substituted Butynes.
A systematic investigation of the bonding in the halogenated butynes demonstrates that the eclipsed conformation actually becomes more stable relative to the staggered form as R becomes larger and less electron-withdrawing. Expand
Origin and nature of bond rotation barriers: a unified view.
  • Shubin Liu
  • Chemistry, Medicine
  • The journal of physical chemistry. A
  • 2013
This work employs two energy partition schemes from density functional theory to investigate the flexible rotation barrier of six molecules with one rotatable dihedral angle and suggests that, even though steric and quantum effects play indispensable roles, it is the electrostatic interaction that governs the barrier height of all these different types of systems. Expand
Rotational barriers in alkanes
Rotational barriers in alkanes play a fundamental role in the stereochemistry and dynamics of alkanes and others such as proteins. Yet, the proper understanding of their origin which is central toExpand
The rotational barrier of ethane and some of its hexasubstituted derivatives in terms of the forces acting on the electron distribution.
The rotational barrier of ethane and several hexasubstituted derivatives, CX3CX3, cannot be explained as a result of any repulsive forces acting on the electron density, although a possible interpretation of the quantum force that balances the EF in stationary states as a measure of traditional Pauli repulsions is examined. Expand


Natural steric analysis of internal rotation barriers
We apply natural bond orbital NBO steric analysis introduced in a . previous article to obtain the steric exchange contribution to the internal rotation barriers . of butane, ethane, and otherExpand
Flexing analysis of ethane internal rotation energetics
A flexing analysis of the ethane barrier energy in terms of structural (ΔEstruct), steric exchange (ΔEsteric), and hyperconjugative charge-transfer (ΔEdeloc) energy contributions has been carried outExpand
Bond-function analysis of rotational barriers: Methanol
Our previous bond‐function analysis of internal rotation in ethane is extended to methanol with the essential result that the dominant contribution to the barrier in these two molecules has the sameExpand
Natural Bond Orbital Analysis of Internal Rotation Barriers and Related Phenomena
The origin of barriers to internal rotation in ethane-like molecules has been investigated with ab initio molecular orbital theory and natural bond orbital (NBO) analysis. The “hyperconjugative”Expand
Quantum-mechanical studies on the origin of barriers to internal rotation about single bonds
An analysis of the forces responsible for internal rotation barriers in ethane-like molecules is carried out in terms of a linear combination of bond orbitals (LCBO) representation of approximateExpand
Natural bond orbital analysis of steric interactions
We describe an ab initio procedure for extracting the Pauli exchange antisymmetry (“steric”) contributions to molecular potential energy in the framework of self-consistent-field molecular orbitalExpand
A study of the ethane internal rotation barrier
Abstract In an effort to deduce the source of the ethane internal rotation barrier, we have investigated the contributions of exchange energy and orthogonality: two effects that are required by theExpand
Origin of rotation and inversion barriers
This paper discusses the origin of barriers to rotation and inversion at the SCF and CI levels by use of the theory of atoms in molecules. The barriers are related to the changes in the attractiveExpand
Comparison of atomic charges derived via different procedures
Atomic charges were obtained from ab initio molecular orbital calculations using a variety of procedures to compare them and assess their utility, and the ability of the charges to reproduce electrostatic potentials was examined. Expand
Organic Chemistry: Structure and Function
"...Peter C. Vollhardt's Organic Chemistry wins hands down ...the book is visually appealing, up-to-date and it is informative and easy to follow." Nature on the Second Edition Organic Chemistry, 3/eExpand