Our bathroom has bedrooms on both sides all the plumbing was on the right wall ,sink toilet and bathtub, we flipped bathtub fixtures to left wall. My question is the wall that it is now on is only 2×4 deep between bathroom and bedroom was there a minimum space that must be in between that wall?
There is no minimum that I am familiar with. A 2 x 4 is fine, and actually quite common. We typically install insulation in the wall to help cut down on the transfer of noise between the two rooms. Other than that, you should be fine.