Question

Why chair conformation of cyclohexane is more stable?

Answer 1

Answer:

The most stable conformation of cyclohexane is the chair form shown to the right. The C-C-C bonds are very close to 109.5o, so it is almost free of angle strain. It is also a fully staggered conformation and so is free of torsional strain.  

Rotate the molecule in the JSMOL image to show this just like a Newman projection so that you can inspect the staggered C-H and C-C bonds.

Answer 2

Explanation:

The most stable conformation of cyclohexane is the chair form

Because it minimizes so-called trans-annular interactions.

Explanation:

In a chair conformation, each face of the cyclohexane ring has 3 axial substituents, whose interaction is sterically unfavourable. This is to be compared with boat and twist-boat conformations whose substituents tend to eclipse each other to give unfavourable steric interactions.