Why is axial more stable than equatorial

A short item in the Journal of Chemical Education offers a nice trick, showing how the chair can be thought of as consisting of an M and a W.

The article is V Dragojlovic, A method for drawing the cyclohexane ring and its substituents. Because axial bonds are parallel to each other, substituents larger than hydrogen generally suffer greater steric crowding when they are oriented axial rather than equatorial. Consequently, substituted cyclohexanes will preferentially adopt conformations in which the larger substituents assume equatorial orientation. When the methyl group in the structure above occupies an axial position it suffers steric crowding by the two axial hydrogens located on the same side of the ring.

The conformation in which the methyl group is equatorial is more stable, and thus the equilibrium lies in this direction. Draw two conformations of cyclohexyl amine C 6 H 11 NH 2.

Indicate axial and equatorial positions. In the following molecule, label which are equatorial and which are axial, then draw the chair flip showing labels 1,2,3. Contributors Dr. Steven Farmer Sonoma State University. Skip to main content. Chapter 3: An Introduction to Organic Compounds. Search for:. Axial and Equatiorial Bonds in Cyclohexane Objectives After completing this section, you should be able to sketch the shorthand structure of cyclohexane, with axial and equatorial hydrogen atoms clearly shown and identified.

Key Terms Make certain that you can define, and use in context, the key terms below. What is a value in organic chemistry? A-Values are numerical values used in the determination of the most stable orientation of atoms in a molecule conformational analysis , as well as a general representation of steric bulk. A-values are derived from energy measurements of the different cyclohexane conformations of a monosubstituted cyclohexane chemical.

Which is the most stable Cycloalkane? Why is anti staggered stable? A staggered conformer is more stable than an eclipsed conformer as the latter involves unfavourable energy interactions between atoms. The staggered conformation with the dihedral angle of 60o , where the H atoms on the 1st carbon are at maximum separation from H atoms on the 2nd carbon. What is the energy difference between the eclipsed conformations?

Torsional strain or eclipsing strain is the name give to the energy difference caused by the increased electrostatic repulsion of eclipsing bonds. What is the most stable Newman projection? The most stable one would have the rear hydrogen in between the front methyl and bromine in a staggered conformation to minimize [lone-pair]-[bonding-electron] repulsions.

Is Gauche more stable than eclipsed? The gauche form is less stable than the anti form due to steric hindrance between the two methyl groups but still is more stable than the eclipsed formations. In this conformation the methyl groups are overlapped with one another. The other eclipsed conformation occurs at the angles of 60 and degrees. Why is the boat conformation less stable? Close proximity of the flagpole hydrogens results in steric strain.

Eclipsing of carbon-hydrogen bonds on adjacent carbon atoms 3 results in torsional strain. When I look down the 1 to 2 carbon and 5 to 4 carbon for the axial position I am getting exactly the Newman projection you have, however, for the equatorial position Newman when I look down the 1 to 2 carbon and 4 to 5 carbon I am not getting the same Newman projection.

Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Notify me via e-mail if anyone answers my comment. This site uses Akismet to reduce spam. Learn how your comment data is processed. Now, the correction to the fib. Is this true? Why might that be? In other words, the equatorial conformer is more stable by 1.

We can use the same approach to measure all of these numbers. More about that in the next post. Advanced References and Further Reading This is a topic commonly taught to undergraduates in Organic Chemistry, and goes along with the discussion on A- values. Electron Diffraction Investigations of Molecular Structures. Results Obtained by the Rotating Sector Method. Hassel, O. Acta Chem. He also proposed that substituents can take two different types of positions on the ring, which he called c- and e-bonds.

He also showed that the conformational analysis of cyclohexanes can be extended to other unsaturated 6-membered rings, such as the pyranoses commonly found in carbohydrates. Barton for his work on conformational analysis. Beckett, Kenneth S. Barton, O. Hassel, K. Pitzer, V.