a b s t r a c t The THz transmission spectra of three trichloroanisole (TCA) compounds (2,3,4-TCA, 2,4,6-TCA and 2,5,6-TCA) are measured using terahertz time-domain spectroscopy (THz-TDS). The spectrum of 2,4,6-TCA in the solid phase displays several discrete absorption peaks over frequency range from 0.1 to 1.5 THz, with significant peaks observed at 0.6, 0.95 and 1.2 THz. A weak absorption peak is observed near 0.2-0.3 THz. Computational chemistry using the B3LYP density functional method is used to study structure and internal rotations in 2,4,6-TCA, where results strongly suggest that frequencies of the CH 3 O-carbon(benzene) internal rotor of the methoxy group correspond to the observed spectra
