Superbases in the gas phase. Part II. Further extension of the basicity scale using acyclic and cyclic guanidines

The superbase gas‐phase scale has been further extended up to proton affinities of ca 1080 kJ mol−1 by use of cyclic and acyclic guanidines and vinamidines. Structural features such as Y‐conjugation, vinylogy and intramolecular ionic hydrogen bonding leading to their superbasic behaviour are analysed. Solvation effects by water and acetonitrile on basicity are discussed. From a correlation pKa(acetonitrile) vs gas‐phase basicity, proton affinity values in the range 1070–1410 kJ mol−1 are predicted for Schwesinger phosphazene compounds.