Relationships between basicity, structure, chemical shift and the charge distribution in resonance-stabilized iminoamines

摘要

Taking formamidine (gas phase proton affinity ≈950 kJ mol ) and guanidine (gas phase proton affintiy ≈990 kJnmolnu00011n) as the prototype iminoamines with resonance-stabilized cations, similar non-cyclic analogs based on anconjugated carbon atom backbone are studied computationally. A simple model of the charge delocalization isndeveloped which predicts theoretical maximum gas-phase proton affinties (PAs) of ≈1114 kJ molnu00011n (unbranched),n1154 kJ molnu00011n (singly-branched) and 1209 kJ molnu00011n (doubly-branched) for such systems. It is also shown that the n1nHnand n15nN chemical shifts of the protons and nitrogens in the imine functions correlate both with basicity and withnatoms-in-molecules multipole moments. The properties of these and related compounds are discussed in the contextnof proton sponges or superbases.