Polarized infrared spectra: Part 1. Stretched polymer method. Fundamental vibrations of some mono- and di-substituted benzenes

Polarized IR spectra of five benzene derivatives (four of C_2v symmetry and one of D_2h symmetry) have been recorded using the stretched polymer method. It has been found that the values of the dichroic ratios depend systematically on the symmetry class of the vibration in question. The IR-active vibrations can thus be unambiguously divided into the correct symmetry classes. The general validity of the method, as well as its value for vibrational analysis, is discussed.