The infrared and Raman spectra of the three crystalline modifications
of hydroquinone (HQ), known as alpha-HQ, beta-HQ and gamma-HQ, have be
en measured and compared with the spectra of HQ solutions. The spectra
have been assigned on the basis of a normal coordinate analysis of th
e molecule and a factor group analysis of the crystals. The hydrogen b
onds are relatively the strongest in beta-HQ, the weakest in gamma-HQ.