engleski

1, 8-Bis(dimethylethyleneguanidino)naphthalene, DMEGN: Tailoring the Basicity of Bisguanidine "Proton Sponges" by Experiment and Theory

1, 8-Bis(dimethylethyleneguanidino)naphthalene (DMEGN), the second example of a peralkyl guanidine “ proton sponge” based on the 1, 8-naphthalene backbone, was prepared and fully characterized. The crystal structure analysis of mono-protonated DMEGN reveals an unsymmetrical intramolecular hydrogen bridge (IHB). A decrease in the basicity with respect to the non-cyclic parent 1, 8-bis(tetramethylguanidino)naphthalene (TMGN) was found. Nevertheless, a new proton sponge provides a new crossbar in the ladder of highly basic neutral organic compounds. A detailed theoretical study of DMEGN and related cyclic guanidines explains this surprising experimental result. Homodesmotic reactions reveal that the intramolecular hydrogen bond (IHB) contributes effectively 10 kcal/mol to proton affinity of DMEGN.

Basicity; Peralkylated guanidines; Protonation; „ Proton sponge“; Hydrogen bonding

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