Knowledge Bank

The pure quadrupole spectra of over twenty covalently bonded chlorine compounds have been observed as solids at liquid-nitrogen temperature. These include chlorides of Sn, As, P, Si, Ge, B, and Sb in addition to the substances described below. Small splittings were frequently seen and were interpreted as crystalline field effects. Approximate quadrupole couplings for chlorine may be computed. The approximate $Cl35$ coupling in solid $CF3Cl$ is -76.18 Mc as compared with the value of -78.05 Mc for the $gas1$ obtained by microwaves. The $Cl35$ coupling in solid chlorine is -108.5 Mc, which indicates that the chemical bond uses a p-orbital with little or no s-hybridization. The magnitude of the couplings increases in the sequence $CH2Cl2,CHFCl2,CHFCl2$, and $CF2Cl2$ as well as in the sequence $CHCl3$ and $CFCl3$. This can be explained by a polarization or inductive effect that makes the C to Cl bond less ionic when highly electronegative F replaces H. The magnitude also increases in the sequence $CH2Cl2,CHCl3$, and $CCl4$, but to a more marked degree than that produced by more highly electronegative F, implying that an explanation in addition to the polarization effect is needed. Work at this Laboratory on chlorine compounds is continuing.