Experimental studies often focus on examining molecules with similar electronic structures, leading to hidden correlations between optical gap and polarizability. In our path towards the general understanding of the relationship between these QM properties, we now examine two different cases: (i) molecules having the same atom-type composition but slightly different chemical compositions and (ii) molecules with the chemical properties fixed while increasing the system size (e.g., oligomers). In Sec. 3.3, we discuss a broader case in which a large subset of CCS is analyzed. Constitution isomers. In general, the functional groups in a molecule govern the nature and order of the molecular orbitals, determining the HOMO-LUMO gap and the orbitals involved in the electronic transitions. To explore the relationship between HOMO-LUMO gap and polarizability as a function of chemical functionality, we present select examples of constitutional isomers, i.e., molecules with the same atomic composition that belong to different substance classes due to the presence of different functional groups.