Microwave, Raman, and infrared spectra; adjusted r(0) structural parameters; conformational stability; and vibrational assignment of germylcyclohexane.

The FT-microwave spectrum of germylcyclohexane, c-C 6 H 11 GeH 3 , has been recorded, and more than 40 transitions for the 70 Ge, 72 Ge, and 74 Ge isotopomers (isotopologues) have been assigned for the chair-equatorial conformer. The heavy atom adjusted r 0 structural parameters have been determined [distances, C γ -C δ = 1.533(3) A, C γ -C β = 1.532(3) A C α -C β = 1.540(3) A, C α -Ge = 1.957(3) A; angles, ∠C γ C δ C β = 111.2(5)°, ∠GeC α C β = 111.1(5)°, with the dihedral angle ∠C γ C δ C β C α = 55.6(10)°]. Raman and/or infrared spectra of gas, liquid, and solid germylcyclohexane have been recorded. The temperature dependency of the Raman spectrum of the conformer pair 712 (equatorial)/683 (axial) cm -1 gives an enthalpy difference of 453 ± 38 cm -1 (1.30 ± 0.11 kcal/mol) with the chair-equatorial conformer the more stable form. At ambient temperature, the abundance of the axial conformer is 11 ± 1%. Substituent effects on the enthalpy difference and structure of monosubstituted cyclohexanes are discussed for a number of molecules.