Knowledge Bank

The barrier to internal rotation and its derivatives (derivatives of the barrier with respect to internal symmetry coordinates) were calculated for $CH3SiH3$ using small basis sets of Slater orbitals with the Hartree-Fock method and also were dettermined from microwave and infrared $spectra.1$. The computed barrier of 1.98 kcal/mole and its $A1$ symmetry derivatives: ---5.57 kcal/\AA mole for the C-Si stretch; ---1.26 kcal/rad. mole for the Si-C-H bend; and ---2.14 kcal/rad. mole for the Si-C-H bend show very good agreement with the experimental values of 1.67 kcal/mole for the barrier and ---5.42 kcal/\AA mole; ---1.16 kcal/rad. mole; and ---1.55 kcal/rad. mole for the three derivatives. The addition of dorbitals on silicon had no significant effect on the calculated results. The barrier derivatives with respect to the C-H and Si-H stretches were assumed to be negligible in the experimental analysis. The change in geometry as the molecule internally rotates and several force constants were also determined both theoretically and experimentally.