GROUP VIBRATIONS OF SUBSTITUTED BENZENES .3. NONPLANAR VIBRATIONS

The normal vibrations of a complete series of chlorinated benzenes and their fully deuterated isotopes are discussed from the potential energy and atomic displacement viewpoints. The interaction of group and nongroup coordinates is discussed in detail. A quantitative expression of the Colthup correlations for in-phase hydrogen deformations has been extended to all hydrogen deformations by considering the relative phase of coordinate pairs. The ring puckering vibrations are shown to have a variable but predictable change in the form of the normal coordinate despite their approximate frequency invariance. Other ring modes and vibrations below 400 cm-1 are described and discussed. Graphs showing the mass dependence of frequencies and potential energy distributions for C6X6 are given. With this data and the potential energy distributions, relative coordinate phase, and the stereo presentations of the Cartesian displacements for the chlorinated benzenes, estimates of the out-of-plane vibrational frequencies of generally substituted molecules may be made. An example is given for p-xylene. © 1968.