Two series of p‐alkyl‐ and p‐alkoxy‐substituted curcuminoids were synthesized. The validity
of the proposed structures was checked on the basis of their high resolution mass spectra as
well as NMR, IR and electronic spectra. The spectra were essentially similar for both series.
NMR, IR and electronic spectra showed that the compounds exist mainly or exclusively as the
enolic tautomer in their solutions. Theoretical study for the electronic spectra was conducted
to account for the origins of the electronic transitions that are responsible for the UV‐VIS
bands. The theoretical calculations were done at the B3LYP/6‐31G(d) level of theory and
predicted that the similarity of the electronic spectra is may be due to the close resemblance
of their molecular orbitals.