STRUCTURAL STUDY AND CONFORMATIONAL-ANALYSIS OF T-BUTYL ETHYL ETHER BY GAS ELECTRON-DIFFRACTION, AB-INITIO CALCULATIONS AND VIBRATIONAL SPECTROSCOPY

The molecular structure and conformational properties of t-butyl ethyl ether were studied by gas electron diffraction. Structural constraints of the data analysis were obtained from HF/4-21G ab initio geometry optimizations, and mean amplitudes of vibration and shrinkage corrections were calculated from vibrational spectra recorded for this analysis. At room temperature the compound exists in a conformational equilibrium of two forms, trans and skew, in a ratio of 70: 30 +/- 24%. Subject to the constraints of the analysis, the following structural parameters were found for the trans conformer: r(g)(O-C)t-Bu = 1.436(3) angstrom; r(g)(O-C)t-Bu - r(g)(O-C)Et = 0.014 angstrom (assumed); r(g)(C-C)t-Bu = 1.532(2) angstrom (averaged value); r(g)(C-C)t-Bu - r(g)(C-C)Et = 0.008 angstrom (assumed); r(g)(C-H) = 1.121(3) angstrom; angle(alpha) C-O-C = 119.9(12)-degrees; angle(alpha)C-C-C(t-Bu) = 111.1 (5)-degrees; angle(alpha)0-C-C(Et) = 109.3(15)-degrees; the tilt angle of the t-butyl group T(alpha) = 4.5(8)-degrees. Parenthesized values are error estimates (3sigma) referring to the last significant digit. The effects of steric repulsion on the structural parameters are discussed.