The Near Ultraviolet Absorption Spectra of 1,4 Bis-(Trifluoromethyl)Benzene and 1,3,5 Tris-(Trifluoromethyl)Benzene

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Abstract
The vapor absorption spectra of 1,4 C6H4(CF3)2 and 1,3,5 C6H3(CF3)3 have been obtained with a Bausch and Lomb Littrow spectrograph. Corresponding solution spectra were obtained with a Beckman DU spectrophotometer. Oscillator strengths f were found to be 12.0×10−3 and 2.1×10−3 for the para di‐ and tri‐substituted compounds, respectively. Both of the vapor spectra are diffuse with the bands of the 1,3,5 compound showing extreme diffuseness. The 0,0 band of the 1,4 bis‐(trifluoromethyl)benzene is located at 37460 cm−1. Progressions and combinations involving the upper state frequencies of 210, 770, and 1020 cm−1 are observed. The 210 and 1020 values are correlated with the observed ground state values of 240 and 1070 cm−1, and these are associated with totally symmetric vibrations. The 1,3,5 tris‐(trifluoromethyl)benzene spectrum is interpreted as a ``forbidden'' one and the bands at 38670 and 38070 cm−1 are assigned as 0,1 and 1,0 bands, respectively. Rough calculations show the 0,0 band to be shifted about 300 cm−1 toward the violet relative to the benzene spectrum.