Ab initio and density functional study of barrier heights for methyl group torsion and conformational deformability in 1,4,6-trimethylnaphthalene

► Ab initio and DFT study of 1,4,6-trimethylnaphthalene (TMN) molecule is presented. ► The barrier heights to methyl group torsions are studied. ► The HOMO and LUMO stability is determined by π∗-σ∗ hyperconjugation. ► Frequencies, IR intensities, Raman activities, and assignments are presented. ► 1,4,6-TMN has higher conformational flexibility compared to naphthalene.