1. At first, you need to do the geometry optimization for the such molecular system. Without any simulation, it is hard (even impossible) to guess what will happen in the structure change. The other way, the stability may also checked by doing the constant temperature MD simulation. See how the structure changes during the equilibrium state of MD simulations.
2. The can draw the total energy as a function of the torsional angel to see how the molecule system is stable or not. For the geometry optimization for each torsional angle, some atoms needs to be fixed to make constraints.
