Final answer:
In a cyclic structure, a substituent can be in an axial position or an equatorial position. It is generally more favorable for a substituent to be in the equatorial position due to steric strain caused by substituents in the axial position.
Step-by-step explanation:
In a cyclic structure, when there is a substituent group attached, it can be either in an axial position or an equatorial position. The axial position refers to a substituent that points upward or downward from the ring, while the equatorial position refers to a substituent that is on the same plane as the ring. In most cases, having a substituent in the axial position can lead to steric strain and destabilize the molecule, making substituents in the equatorial position more favorable. This is because the substituents in the axial position can experience steric interactions with other groups on the same face of the ring.