Microwave Spectrum, Structure, Quadrupole Coupling Constants, and Barrier to Internal Rotation of Chloromethylsilane

Observations of the microwave spectra of seven ground-state species and three first excited torsional state species of CH2ClSiH3 are reported. From an analysis of the moments of inertia of the various species structural parameters are deduced as follows: bond distances; CCl=1.788 A, CSi=1.889 A, CH=1.096 A, SiH=1.477 A, and bond angles; SiCCl=109.3°, SiCH=109.3°, HSiH=110.6°, and HCH=107.5°. An analysis of the hyperfine splitting leads to quadrupole coupling parameters χCCl bond=—68.7 Mc, ηCCl bond=0.048, if it is assumed that the CCl bond direction forms one principal axis of the quadrupole tensor; and χCCl bond=—72.0 Mc if it is assumed that the quadrupole tensor is cylindrically symmetric. Analysis of splittings in the first excited torsional state indicate that the height of the potential barrier hindering internal rotation of the SiH3 group is 2.55 kcal/mole.