Hydroquinones constitute a family of antioxidants, but are also known as electron donor molecules in charge transfer complexes. Raman and IR spectra of 1,4-dihydroquinone (H2Q) and its derivatives, 2,5-dichloro-1,4-dihydroquinone (H2QCl2)
and 2-methoxy-1,4-dihydroquinone (H2QOCH3) in solid form have been recorded. Theoretical calculations using DFT
(B3LYP) methods have been performed giving optimized structures, energies and harmonic vibrational frequencies. The
comparison between the vibrational frequencies calculated and scaled with Raman and FT-IR experimental values shows
good agreement. The infuence of the substitutions on the electron donor capacity, geometrical parameters and normal modes
of vibrations have been discussed. The presence of –Cl group increases the O–H bond length and decreases the electron donor
capacity and inversely for the presence of –OCH3. The O–H stretching vibrations shift to higher wave numbers in H2QCl2
and H2QOCH3. The aromatic C–H stretching vibrations are not much afected by the presence of –Cl and –OCH3. The C–C
and C=C stretching vibrations shift to higher wave numbers in H2QCl2 and shift to lower wave numbers in H2QOCH3. These
studies show the infuences of substitutions on molecular properties of hydroquinones.
Keywords 1,4-Dihydroquinone · DFT calculations · Symmetry · IR · Raman

1,4-Dihydroquinone, DFT calculations, Symmetry, IR, Raman