What is axial and equatorial hydrogen?

In cyclohexane, a common cyclic hydrocarbon, two types of hydrogens are present due to the chair conformation of the molecule: axial hydrogens and equatorial hydrogens.

1. Axial Hydrogens: Axial hydrogens are those oriented vertically concerning the plane of the cyclohexane ring. They project either upwards or downwards from the carbon atoms of the ring. These hydrogens are positioned parallel to the imaginary axis passing through the centre of the ring. Axial hydrogens are relatively less stable due to steric hindrance and experience greater repulsion from neighbouring groups.

2. Equatorial Hydrogens: Equatorial hydrogens are oriented horizontally concerning the plane of the cyclohexane ring. They extend outward from the carbon atoms of the ring in a direction roughly perpendicular to the ring plane. Equatorial hydrogens are positioned around the equator of the cyclohexane ring and are relatively more stable than axial hydrogens. They experience less steric hindrance and exhibit lower repulsion from neighbouring groups.

Difference between Axial and Equatorial Hydrogen:

The main differences between axial and equatorial hydrogens in cyclohexane are given in the following table:

In the chair conformation of cyclohexane, each carbon atom is attached to one axial hydrogen and two equatorial hydrogens. The distribution of axial and equatorial hydrogens contributes to the molecule’s stability and influences its physical and chemical properties.