The UV absorption spectra of the trichlorobenzenes and the higher chlorinated benzenes in the gas phase and in n-hexane solution.

Absolute absorption cross sections are determined for the three isometric trichlorobenzenes in the gas phase in the region from 33000 to 60000 cm-1, and relative absorption in the region from 40000 to 60000 cm-1. Spectra in n-hexane solution are determined for comparison. The spectra in the gas phase are compared to the spectra in solution and to spectra of the analogous fluoro compounds. With respect to band shifts a comparison is made to theoretical considerations (developed for spectra in solution) and a revised set of parameters for gas-phase spectra is derived. Vapor pressures for the tetrachlorobenzenes and for pentachlorobenzene are estimated at room temperature from the observed absorption intensities. (ITA