A variety of terminal chain modifications were made by placing/removing the electro-negative oxygen atom to either or both sides of the rigid core of the benzylidene aniline compounds, the chosen alkyl chain lengths were n=5 and m=16. The mesomorphic properties were determined by polarizing thermal microscopy (TM) and differential scanning calorimetry (DSC). They exhibit two mono-variant and two di-variant phase sequences. The results are discussed in light of the depression in melting temperature, elevation of clearing temperature, and quenching of liquid-crystalline phases as a function of influence of oxygen with the end alkyl chain length.