engleski

Substituted troponimines: when aromatization of the conjugate acid leads to very strong neutral organic superbases

In the present study, N-methyl-2, 4, 6- cycloheptatriene-1-imine (Troponimine) with (Me)2N- and MeO- substituents have been investigated theoretically to evaluate their suitability as a new neutral organic superbase. To introduce the aforementioned system, thermochemical parameters such as gas basicity and proton affinity have been calculated along with their pKBH+ values in acetonitrile. Results revealed that all studied troponimine derivatives are more basic than 1, 8- bis(dimethylamino)-naphthalene whose gas phase basicity of 237 kcal mol-1 is considered to be the borderline between ordinary bases and superbases. However, the most important finding is that some of the proposed troponeimines are much stronger bases than the well-established cyclopropenimine superbases. Origin of troponimine basicity is elucidated through NICS calculations which reveal that troponimines become aromatic upon protonation. AIM analyses revealed that the hydrogen bond could also contribute to the basicity if a suitable substituent is located on the adjacent of the imine group of the troponimine.

neutral organic superbases ; troponimines ; proton affinity ; pKa values

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