10.1021/jp801346v.s001 Yuri V. Vishnevskiy Yuri V. Vishnevskiy Natalja Vogt Natalja Vogt Jürgen Vogt Jürgen Vogt Anatolii N. Rykov Anatolii N. Rykov Vladimir V. Kuznetsov Vladimir V. Kuznetsov Nina N. Makhova Nina N. Makhova Lev V. Vilkov Lev V. Vilkov Molecular Structure of 1,5-Diazabicyclo[3.1.0]hexane as Determined by Gas Electron Diffraction and Quantum-Chemical Calculations American Chemical Society 2008 DABH MP 2 calculations boat conformation Gas Electron Diffraction NBO analysis 2008-06-12 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Molecular_Structure_of_1_5_Diazabicyclo_3_1_0_hexane_as_Determined_by_Gas_Electron_Diffraction_and_Quantum_Chemical_Calculations/2934100 The equilibrium molecular structure and conformation of 1,5-diazabicyclo[3.1.0]hexane (DABH) has been studied by the gas-phase electron-diffraction method at 20 °C and quantum-chemical calculations. Three possible conformations of DABH were considered: boat, chair, and twist. According to the experimental and theoretical results, DABH exists exclusively as a boat conformation of <i>C<sub>s</sub></i> symmetry at the temperature of the experiment. The MP2 calculations predict the stable chair and twist conformations to be 3.8 and 49.5 kcal mol<sup>−1</sup> above the boat form, respectively. The most important semi-experimental geometrical parameters of DABH (<i>r</i><sub>e</sub>, Å and ∠<sub>e</sub>, deg) are (N1−N5) = 1.506(13), (N1−C6) = 1.442(2), (N1−C2) = 1.469(4), (C2−C3) = 1.524(7), (C6−N1−C2) = 114.8(8), (N5−N1−C2) = 107.7(4), (N1−C2−C3) = 106.5(9), and (C2−C3−C4) = 104.0(10). The natural bond orbital (NBO) analysis has shown that the most important stabilization factor in the boat conformation is the <i>n</i>(N) → σ*(C−C) anomeric effect. The geometry calculations and NBO analysis have been performed also for the bicyclohexane molecule.