We try to explain the causes of the disappearance of the nematic phase by changing the position of the nitrogen in 2,5-disubsituted pyridine derivatives by quantum mechanical theory. The findings explain that the electrostatic interactions along with shape anisotropy are causes of sequential appearances/disappearances of liquid crystal phases. The antiparallel or parallel orientations also play a crucial role in the formation of liquid crystal phases. The study reveals the strong alignment of mesogens in the liquid crystal phase.