The structure of liquid methylamine and solutions of lithium in methylamine

The technique of hydrogen/deuterium isotopic substitution in neutron diffraction has been used to measure the intra- and intermolecular correlations in liquid methylamine, and 2 and 8 MPM (mole percent metal) lithium methylamine solutions. We find that pure methylamine forms only one strong hydrogen bond per molecule, with evidence for weaker orientations towards the methyl group. As one introduces lithium metal, the intramolecular structure of the solvent is unaltered. However, intermolecular hydrogen bonding is progressively disrupted as the concentration of (solvated) cations and excess electrons increases. Comparison of the total structure factors for 0, 2, 8 and 20 MPM lithium methylamine solutions shows that the greatest shift in the position of the principal peak occurs between 8 and 20 MPM. This can be correlated to the electron delocalization associated with the non-metal-metal transition.