Difference Between Chair and Boat Conformation

The key difference between chair and boat conformation is that chair conformation has low energy, whereas boat conformation has high energy.

The terms chair conformation and boat conformation come under organic chemistry, and they are mainly applicable to cyclohexane. These are two different structures in which the cyclohexane molecule can exist, but they have different stabilities depending on the energy of their structure.

CONTENTS

1. Overview and Key Difference
2. What is Chair Conformation 
3. What is Boat Conformation 
4. Side by Side Comparison – Chair vs Boat Conformation in Tabular Form
5. Summary

What is Chair Conformation

Chair conformation is the most stable structure of cyclohexane. This is because it has low energy. Usually, at room temperature (around 25°C), all the molecules of cyclohexane occur in chair conformation. If there is a mixture of different structures of the same compound at this temperature, around 99.99% of the molecules convert into chair conformation. When considering the symmetry of this molecule, we can name it as D_3d. Here, all the carbon centres are equivalent.

There are six hydrogen atoms that occur in the axial position. The other six hydrogen atoms are located nearly perpendicular to the symmetry axis, which is the equatorial position. If we consider the carbon atoms, each of them contains two hydrogen atoms: one hydrogen atom “up” and the other one “down”. There is little torsional strain because C-H bonds are in staggered conformation.

What is Boat Conformation?

Boat conformation is a less stable structure of cyclohexane since this structure has high energy. There is a considerable steric strain in this structure because of the interaction between two flagpole hydrogens, and there is a considerable torsional strain as well. These strains also cause the unstable nature of the boat conformation. The symmetry of this structure is named C_2v.

Moreover, the boat conformation tends to convert into the boat-twist conformation spontaneously. Its symmetry is D₂. This structure appears as a slight twist of the boat conformation. Rapid cooling of the cyclohexane converts boat conformation into boat-twist conformation, which converts into chair conformation upon heating.

What is the Difference Between Chair and Boat Conformation?

The terms chair conformation and boat conformation apply mainly to cyclohexane. The key difference between chair and boat conformation is that a chair conformation has low energy, whereas boat conformation has high energy. Due to this reason, chair conformation is stable than boat conformation. Usually, chair conformation is the most stable conformation, and at room temperature, about 99.99% of cyclohexane in a mixture of different conformation exists in this conformation.

Moreover, the symmetry of chair conformation is D_3d while boat symmetry has the symmetry C_2v. Besides, boat conformation tends to convert into the boat-twist conformation spontaneously. However, both these structures tend to convert into the chair conformation upon heating. Furthermore, another difference between chair and boat conformation is that the torsional strain and steric hindrance in chair conformation are low compared to boat conformation.

Summary – Chair vs Boat Conformation

The terms chair conformation and boat conformation apply mainly to cyclohexane. The key difference between chair and boat conformation is that a chair conformation has low energy, whereas a boat conformation has high energy. Therefore, the chair conformation is more stable than boat conformation at room temperature. Generally, the chair conformation is the most stable structure of cyclohexane at room temperature.

Reference:

1. “Cyclohexane Conformation.” Wikipedia, Wikimedia Foundation, 24 Nov. 2019, Available here.
2. “Boat Conformation.” Chemistry LibreTexts, Libretexts, 5 June 2019, Available here.
3. “Conformation of Cyclohexane.” Chemistry LibreTexts, Libretexts, 5 June 2019, Available here.

Image Courtesy:

1. “Cyclohexane-chair-colour-coded-3D-balls” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia
2. “Cyclohexane ring flip and relative conformation energies” By Keministi – Own work (CC0) via Commons Wikimedia