In order to investi- gate these intensive changes, the IR spectra at each specific temperature are isolated in Fig. 3. The transformation of ac- etaminophen from solid to liquid states might broaden the IR spectrum. Moreover, the shift of the CϭO stretching and N–H bending bands in acetaminophen molecule also indi- cated the weakness of intermolecular hydrogen bonding in the liquid state (Fig. 3a→Fig. 3b).