trans-dimethylcyclohexane.html

What is the difference in energy between the two chair conformations of trans-1,4-dimethylcyclohexane? In the lefthand structure the two blue methyl groups are both axial on opposite faces of the ring. Each side of the ring is effectively an axial methyl cyclohexane. Therefore, the total energy is 1.8 + 1.8 = 3.6 kcal/mol. In other words, there is a total of four gauche butane interactions. Chair interconversion produces a chair conformation having two (red) methyl groups. Since each of these methyl groups is equatorial and there is no interaction between the methyl groups, the energy of this conformation is taken as 0 kcal/mol. The difference in energy is 3.6 kcal/mol with the diequatorial conformation prevailing.