Prev. Article Next Article Table of Contents

Article

A Simple Molecular Orbital Treatment of the Barrier to Internal Rotation in the Ethane Molecule

Citing Articles

Your current credentials do not allow retrieval of the full text.

Purchase the full-text

PDF/HTML,
figures/images,
references and tables,
(where available)

Derek W. Smith

University of Waikato, Department of Chemistry, Te Thare Wananga o Waikato, Private Bag 3105, Hamilton, New Zealand

J. Chem. Educ., 1998, 75 (7), p 907

DOI: 10.1021/ed075p907

Publication Date (Web): July 1, 1998

Section:

History, Education, and Documentation

Abstract

The origin of the barrier to internal rotation in the ethane molecule is explored in terms of elementary molecular orbital (MO) considerations. Emphasis is placed on the antibonding effect, i.e. the result that an antibonding MO is more destabilized than its bonding counterpart is stabilized, relative to the parent atomic orbitals (AOs). It is shown that, in the case of two equivalent AOs, this effect is approximately proportional to the square of the overlap integral. By constructing the ethane Mos from those of two methyl fragments, it is shown that the most important orbital energy changes consequent upon rotation about the C-C bond can be expressed in terms of the antibonding effect arising from the filled twofold-degenerate p-bonding and -antibonding MOs. This can be reduced to the dependence on the rotation angle of the vicinal H-H overlap integrals, which are calculated explicitly, showing that the antibonding effect is minimised in the staggered conformation.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Organic Chemistry

Keywords (Subject):

Covalent Bonding

View: Hi-Res PDF | PDF w/ Links

Citing Articles

Citation data is made available by participants in CrossRef's Cited-by Linking service. For a more comprehensive list of citations to this article, users are encouraged to perform a search in SciFinder.

This article has been cited by 9 ACS Journal articles (5 most recent appear below).

Determination of the Rotational Barrier in Ethane by Vibrational Spectroscopy and Statistical Thermodynamics
Gianfranco Ercolani
Journal of Chemical Education2005 82 (11), 1703
- Determination of the Rotational Barrier in Ethane by Vibrational Spectroscopy and Statistical Thermodynamics
  Gianfranco Ercolani
  Journal of Chemical Education2005 82 (11), 1703
  In a previous article in this Journal (J. Chem. Educ. 2000, 77, 1495) we introduced a numerical method, namely, the finite-difference boundary-value method, for the solution of the one-dimensional Schrödinger equation and illustrated its application to ...
  Abstract | Hi-Res PDF | PDF w/ Links
Effects of Exchange Energy and Spin-Orbit Coupling on Bond Energies
Derek W. Smith
Journal of Chemical Education2004 81 (6), 886
- Effects of Exchange Energy and Spin-Orbit Coupling on Bond Energies
  Derek W. Smith
  Journal of Chemical Education2004 81 (6), 886
  It is shown that the ground states of atoms having pn configurations are stabilized by exchange energy (n = 2, 3, or 4) and/or spin–orbit coupling (n = 1, 2, 4, or 5). The extent of such stabilization is given by the barycenter of all states arising from ...
  Abstract | Hi-Res PDF | PDF w/ Links
Numerical Evaluation of Energy Levels and Wave Functions for Hindered Internal Rotation
Gianfranco Ercolani
Journal of Chemical Education2000 77 (11), 1495
- Numerical Evaluation of Energy Levels and Wave Functions for Hindered Internal Rotation
  Gianfranco Ercolani
  Journal of Chemical Education2000 77 (11), 1495
  A numerical procedure for the solution of the one-dimensional Schrödinger equation (the finite-difference boundary-value method), especially suited for problems having periodic nature, is presented and applied to the problem of hindered internal rotation. ...
  Abstract | Hi-Res PDF | PDF w/ Links
The Antibonding Effect
Derek W. Smith
Journal of Chemical Education2000 77 (6), 780
- The Antibonding Effect
  Derek W. Smith
  Journal of Chemical Education2000 77 (6), 780
  It is shown that the consequence of filling both a bonding molecular orbital (MO) and its antibonding counterpart leads to a total orbital energy greater than that of the separated atoms. The resulting antibonding effect can be buffered if the antibonding ...
  Abstract | Hi-Res PDF | PDF w/ Links
Capsaicin Hazard
Paul E. Vorndam
Journal of Chemical Education2000 77 (4), 444
- Capsaicin Hazard
  Paul E. Vorndam
  Journal of Chemical Education2000 77 (4), 444
  Warning on handling or working with capsaicin.
  Abstract | Hi-Res PDF | PDF w/ Links