Probing the influence of solvent effects on the conformational behavior of 1,3-diazacyclohexane systems.

The conformational behavior of a 1,3-diazacyclohexane system has been investigated using the DFT B3LYP/6-311+G** level of theory. The structural parameters and relative energies predicted that anomeric effects are operative in the conformations of 1,3-diazacyclohexane. The stability of conformers predicted in the solvent continuum model (water and acetonitrile) is similar to the gas-phase results. The explicit water molecules stabilized the least-stable conformer, and the predictive trend is opposite to that of the gas-phase results. The stability of the conformers in the gas phase is a compromise between avoiding repulsions and maximizing hyperconjugative stabilization. The NBO analysis suggests that the interactions of explicit solvent molecules with 1,3-diazacyclohexane conformers attenuate the anomeric stabilization. The hydrogen-bonding interactions of explicit solvent molecules with 1,3-diazacyclohexane swamped the anomeric effects to alter the conformational stability compared to the gas-phase and solvent continuum model studies.