engleski

Computer Aided Design of Organic Superbases - The Role of Intramolecular Hydrogen Bonding

The role of intramolecular hydrogen bonding (IMHB) in determining the proton affinities and basicities of some bis(tetramethylguanidine) systems is examined. For this purpose a series of molecular backbone moieties serving as carriers of the bis(tetramethylguanidine) crowns are explored. It was found that the best backbones are provided by phenanthrene and 9, 10–dihidrophenanthrene giving rise to the proton affinity as large as 268.2 and 266.8 kcal/mol, respectively. The corresponding pKa values in acetonitrile are 29.0 and 28.8 implying that these two compounds (6(bs) and 5(bs)) are candidates for powerful superbases. Their intramolecular hydrogen bond strengths are = 19 kcal/mol, which result inter alia from the partial protonation of the vis–?–vis guanidine group.

organic superbase; hydrogen bond; proton affinity

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