Abstract
The modified first Zagreb connection index (ZC1*) 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. Trinajstic, A novel/old modification of the first Zagreb index, Mol. Inform. 37 (2018) 1800008], it was observed that the molecular descriptor ZC1* correlates well with the entropy and acentric factor of octane isomers. In this article, the molecules with the first three maximal ZC1* values as well as the first three minimal ZC1* 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.