Proton affinities of 2-iminoimidazolines with bulky N-alkyl-substituents

The gas-phase proton affinities of 2-iminoimidazolines with bulky substituents on the ring-nitrogen atoms are investigated by the kinetic method. The experimental results are complemented by calculations using density functional theory. It turns out that the title compounds can be termed as superbases with the largest proton affinities ranging up to 260 kcal mol−1.

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► The fragmentation patterns of sterically crowded 2-iminoimidazolines have been measured.
► The proton affinities of these 2-iminoimidazolines have been determined experimentally.
► The normal and the extended kinetic method have been used.
► The experimental data are supported by DFT calculations of the proton affinities.
► A phosphazene base is used as an independent reference.