Hydrogen Bonding Modulation Via Aromaticity
Bailey, John P.
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The capability of modulated hydrogen bonding is something of significant interest to the chemical and biological communities due to the wide array of hydrogen bonding systems present which may be altered for beneficial purposes. The experimental data yielded by our method provides evidence that the capability for hydrogen bonding may altered by the changing aromatic character of H-bonded molecule that can occur as a result of resonance assisted hydrogen bonding (RAHB) . 1-methyl-1,3-dihydro-2H-imidizol-2-one (1) which increased aromatic character in its H-bonding dimer form was compared against 2-Methylimidazolidinone (1’) which retained its aromatic character, and when the dimerization enthalpies were calculated via 1H NMR 1 was 2.4±0.2 kcal/mol stronger than 1’. 2,3-dihydro-1H-imidazo[1,2-a]imidazole (2) which lost aromatic character in its dimer system was similarly compared against 2,3,5,6- tetrahydro-1H-imidazo[1,2-a]imidazole (2’) which had no aromatic shift and showed weakened ΔH by 2.0±0.2 kcal/mol.