Abstract
Triisopropylnaphthalene isomers (TriIPN) formed in the isopropylation of naphthalene (NP) and 2,6-/2,7-diisopropylnaphthalenes (2,6-/2,7-DIPN) over BEA300 and FAU80 zeolites with 300 and 80 of SiO2/Al2O3 ratio, respectively, were assigned by gas chromatography based on their reaction pathways: this is the first systematic assignment of four TriIPN isomers: 1,3,7-, 1,3,6-, 1,4,6-, and 1,3,5-isomers. 1,3,7- and 1,3,6-TriIPN were assigned from their predominant formation in the isopropylation of 2,6-/2,7-DIPN over BEA300, respectively. 1,4,6- and 1,3,5-TriIPN were assigned from reaction pathway of the isopropylation of NP over FAU80 at lower temperatures and/or in the initial stages: 1,4,6-TriIPN are formed predominantly from 1,4- and 1,7-DIPN: 1,4-DIPN is a major precursor for 1,4,6-TriIPN and 1,7-DIPN also gives 1,4,6-DIPN by the preferential attack of isopropyl carbenium cation to electron-rich C-4-position. DFT calculation confirmed that high electron density at the C-4-position of 1,7-DIPN compared to the C-5-position plays a critical role in the predominant formation of 1,4,6-TriIPN.