Alkanes with the First Three Maximal/Minimal Modified First Zagreb Connection Indices.

The modified first Zagreb connection index ( Z C 1 * ) is a molecular descriptor, which was initially appeared within a formula of the total electron energy of alternant hydrocarbons in 1972. In a recent paper [A. Ali, N. Trinajstić, A novel/old modification of the first Zagreb index, Mol. Inform. 37 (2018) 1800008], it was observed that the molecular descriptor Z C 1 * correlates well with the entropy and acentric factor of octane isomers. In this article, the molecules with the first three maximal Z C 1 * values as well as the first three minimal Z C 1 * values are determined from the family of all alkanes with n carbon atoms, for n ≥ 6 . This extends the main results of the aforementioned paper.