Abstract The 3 Δ-deuterium isotope effects of partially and fully deuteriated tert-butyl groups on the 13 C NMR spectra of tert-butylbenzene and derivatives are discussed in detail. It is shown that they correlate with the chemical shift of C-1 of the aromatic ring. It has been demonstrated that when deuterium is replaced with some other substituents, the SCS values of these substituents show a parallel behaviour to the deuterium isotope effects. It is ...