S-Trans

S-Trans Definition:

A conformation of a conjugated diene in which the disposition of the two p bonds with regard to the connecting single bond is trans-like (a dihedral angle of 180°).

S-Trans Explained:

When a molecule forms a ring that “locks” it to a certain extent before they are fastened it together, it can be twisted. But once fastened, there are practical limits to how much it can turn inside-out. If the radius is too small or if the martial it is made of is stiff it becomes “locked”. It can’t turn it inside out anymore.

It all depends on the position, if it is the opposite or the ring it is said to be trans and if it is in the same direction then is it cis.