Molecular structure and conformational properties of N-cyclohexylpiperidine as studied by gas-phase electron diffraction, mass spectrometry, IR spectroscopy and quantum chemical calculations

Abstract

Conformational properties and molecular structure of N-cyclohexylpiperidine (NCHP) were studied by quantum chemical calculations (DFT-B3LYP and MP2), gas-phase electron diffraction (GED–MS) and IR spectroscopy. NCHP may exist in at least eight conformeric forms that differ by their axial and/or equatorial positions and the relative orientation of the two rings. Two of these conformers were found to dominate in the gas phase at room temperature: The most stable conformer, I, has both rings in equatorial positions and oriented perpendicularly relative to each other. The less abundant conformer, II, has the rings in equatorial position and nearly parallel equatorial to each other. Structural parameters are given for these conformers. The experimental and theoretical methods indicate that conformers with equatorial position of the cyclohexane ring relative to the piperidine ring are more stable in a gas and liquid phases