Knowledge Bank

Kinetic and potential energy matrix elements are given in analytical form for the vibrations of balanced, non-axially symmetric $CX2NO2$ molecules. The matrix elements may be easily converted for use in $CX2YZ2$ molecules with symmetrically planar $CYZ2.C2r$ symmetry was used and its applicability examined. Potential energy constants obtained for $CF3NO2,CCl3NO2$, and $CBr3NO2$ yield calculated vibrational frequencies which agree with observed values to over 98%. The transferbility and uniquencess of the constants and the significance of the agreement is discussed. Geometry and s-character are examined in terms of the normal coordinate calculation. An empirical relationship is proposed for connecting electronegativity and atomic mass with changes in $YZ2$ deformation frequencies.