I just read that the reason molecules rotate plane polarized light is because the light interacts with the electron cloud of the molecule. That makes sense but why aren't achiral molecules optically active? Achiral molecules have electron clouds too so why don't their electron clouds cause optical rotation? As an example, lets say a 2 carbon alkene with 4 different substituents i.e. 1,1-hydroxychloro-2,2-iodoaminoethylene. This molecule is achiral but it has an irregular shaped electron cloud so why doesn't plane polarized light rotate when it interacts with that irregular shaped electron cloud?