Studies with Vibrating Mechanical Models II. The Series: C6H5Cl–C6Cl6

Abstract

Mechanical models have been constructed for the following molecules based on the Pauling resonance formula for benzene: C₆H₆; C₆H₅Cl; o‐, m‐, p‐C₆H₄Cl₂; (1, 2, 3)‐, (1, 2, 4)‐, (1, 3, 5)‐C₆H₃Cl₃; C₆Cl₆. The mechanical spectra of these models have been observed and compared with the Raman spectra. The shifts in frequency observed in passing down the series are the same in both mechanical and Raman spectra in a number of cases. This makes possible the identification of several of the lines connected with the motions of the chlorine atoms and of the line at 992 cm^—1 associated with the symmetrical expansion of the benzene ring. The types of motion show an evolution from the symmetrical group of C₆H₆, which can be correlated with group theory, through the various doublets and triplets associated with the less symmetrical intermediate compounds, to the group connected with C₆Cl₆ which is similar to that of C₆H₆ except for the inversion of frequency order due to the increased mass of the substituent atoms