Cyclohexane Conformations: Chair, Boat & Twist-Boat

Cyclohexane Conformations: Chair, Boat & Twist-Boat
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  • 0:04 Cyclohexane Conformations
  • 0:48 Chair Confirmation
  • 2:02 Boat Confirmation
  • 2:41 Twist-Boat Confirmation
  • 3:27 Lesson Summary
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Lesson Transcript
Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

The proper conformation of cyclohexane is not a hexane. In this lesson, we will learn about the three conformations that cyclohexane can form: chair, boat and twist-boat.

Cyclohexane Conformations

When drawing cyclohexane molecules it's easy to draw them as a simple hexane, but in reality this image doesn't depict the actual structure very well. A hexane has bond angles of 120o, but bond angles between carbon atoms are preferentially 109.5o. The chair, boat, and twist-boat conformations show the angles much closer to the ideal 109.5o, and these are the shapes that most cyclohexane molecules are actually found to be in.

The three conformations that cyclohexane can form
cyclohexane conformations

The lowest energy conformation is the chair conformation; thus, it is the most popular. Twist-boat and boat conformations are higher in energy than chair and are similar in energy levels, although boat is slightly higher than twist-boat.

Chair Conformation

In the chair conformation there are two planes, with carbon atoms alternating, making carbon atoms 1, 3, and 5 in one plane and carbon atoms 2, 4, and 6 in another plane. There are two possible positions for hydrogen atoms or other substituents to be located: axial and equatorial. The axial position is not parallel to any of the carbon-carbon bonds while the equatorial position is parallel to one or more of the carbon-carbon bonds.

If we start numbering the carbon atoms from the top right corner as carbon 1, then carbon atoms 1, 3, and 5 have the axial positions as the carbon pointing 'up' while equatorial is pointing 'down'. Carbon atoms 2, 4, and 6 have the axial position as the carbon point 'down' while the equatorial is pointing 'up'. This means that if we simply turn the molecule slightly, the hydrogen atoms pointing up will now be pointing down because each atom keeps the axial or equatorial orientation, not the 'up' and 'down' orientation:


Red represent axial positions and blue represent equatorial positions
Axial and equatorial bonds


There is very little strain in this conformation, which is why it is so stable. With the axial and equatorial bonds alternating up and down, there is very little interference between molecules. Looking at the Newman projection of the chair conformation helps to see how there is little interference:


The Newman projection for the chair conformation
Newman for chair


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