Infrared spectra of the monomethyl and dimethyl naphthalenes

The infrared spectra of the ten isomeric dimethyl naphthalenes and the two monomethyl naphthalenes have been observed in the CH stretch, 2000-1650 and the 700-400 cm⁻¹ regions. The effect on the aromatic CH stretching vibrations due to the position of the methyl groups on the naphthalene nucleus is outlined. The position of the methyl groups can be established from data obtained from the 2000-1650 and the 700-400 cm⁻¹ regions. Effect on band frequencies and intensities by replacement of methyl by phenyl group in the monosubstituted naphthalene is discussed.