A STUDY BY GAS-PHASE ELECTRON-DIFFRACTION OF TERT-BUTYLDIMETHYLSILANOL AND ITS HEMIHYDRATE

The molecular structures of tert-butyldimethylsilanol and its hemihydr ate in the gas phase have been determined by electron diffraction. The two diffraction patterns are indistinguishable, indicating that the h ydrate is essentially completely dissociated in the vapour phase under the conditions of the experiment. The most significant geometrical pa rameters for Bu'Me(2)SiOH (r(a)) are: r(Si-C) (mean) 188.4(1) pm r(Si- O) 166.2(3) pm, r(C-C) 154.6(2) pm, angle SiCC 107.8(2)degrees, angle CBuSiO 106.8(17)degrees, angle CBuSiCMe 112.3(10)degrees and angle CMe SiO 109.2(10)degrees. The molecule adopts an almost perfectly staggere d conformation about the SiC(butyl) bond.