Knowledge Bank

A modified Urey-Bradley type of force field has been used as the basis for the determination of satisfactory and consistent potential constants for $C2F4$, $C2Cl4$, and $C2Br4$. These force constants were obtained by the joint application of least-squares and high-speed digital computation methods. The frequency fit for these three molecules is generally quite good. In the course of this work it became possible to revise existing assignments for $C2Cl4$, and $C2Br4$, and to adduce evidence which strongly suggests that all the fundamentals have now been correctly located.