A huge mass of possible molecular variants often forms a puzzle on their identity and integrity to the processes which can be resolved by adopting a concrete selection procedure significant for it. This further relies on its relation with some phenomena on microscopic structure and macroscopic behavior. This study recognizes the numerous approaches to answer it on the grounds of Thermodynamics for Ionic Liquids (ILs) and conception of middleman in additivity phenomenon through molecular tailoring and validated dataset, wherein Wada’s theory for molecular compressibility, A is found inconsistent and thus redefined. ILs are found to be divergent into two groups, depending upon the cationic integration rather than anionic, on analysis of close intimacy of the molecular sound velocity, R to the molecular weight. Moreover, the study presents ILs in contrast to molecular fluids and physiochemical nature in terms of Jacobson’s relation and Mark’s study on molecular fluids. The applicability of Newton-Laplace relation has also been deduced The missing links in persisting theories are explored quantitatively and structural descriptors are estimated for structural variability of –CH2/-CH3 commonly found in ILs. It seems quite interesting to visualize the appendages like benzyl, methylene and methyl in molecular skeleton being the source of drastic effects on the studied behaviors. By far, these can, more or less, aid in solving molecular puzzle of accessing ionic liquids’ potential of structural variability for task-specific applications, say fluid mechanics, organic synthesis, reaction kinetics, antimicrobial activity and CO2 capture and sequestration.