Determination of the tautomeric composition of adenine in the gas phase by vibrational spectroscopy methods: I. Analysis of IR spectra

Aromaticity from the Viewpoint of Molecular Geometry: Application to Planar Systems

“…The 9 H -amino tautomer is more stable in all phases. In the gas phase, the energy gap between the canonical 9 H -structure and the less preferred 7 H - and 3 H -tautomers is about 7.5 kcal/mol, while this gap is reduced to 2.5 kcal/mol in water, but the order of stability is retained; 7 H - and 3 H -tautomers are energetically very close. − Theoretical results are in agreement with experimental data. − It is also found that the 9 H ,1 H + form of adenine (9 H adenine protonated at the position N1) dominates in water along with the 9 H and 7 H ones. − …”

Geometric and energetic consequences of prototropy for adenine and its structural models – a review

“…8). 7,99,103,118,122 Among them A-N9H-N10H is the global minimum at all computational levels in the gas phase, 7,73,[75][76][77]99,101,103,110,118,119,122,128,132 in low-temperature Kr, Ar, and Ne matrices, 73,[75][76][77]101,132 in microhydrated environment and in bulk water. 7,99,103,118,122 Among them A-N9H-N10H is the global minimum at all computational levels in the gas phase, 7,73,[75][76][77]99,101,103,110,118,119,122,128,132 in low-temperature Kr, Ar, and Ne matrices, 73,[75][76][77]…”

“…7 Indeed, maximum eight NH-NHs can be considered for neutral adenine. 7,99,103,118,122 Among them A-N9H-N10H is the global minimum at all computational levels in the gas phase, 7,73,[75][76][77]99,101,103,110,118,119,122,128,132 in low-temperature Kr, Ar, and Ne matrices, 73,[75][76][77]101,132 in microhydrated environment and in bulk water. 7,109,117,118,123,129 Theoretical investigations, predicting co-existence of three tautomers {A-N9H-N10H (97.5%), A-N7H-N10H (2.5%), and A-N3H-N10H (0.02%)} in bulk water, 7,118 are in good agreement with NMR experiments Scheme 3 Favored redox processes for 4-aminopyrimidine in the gas phase (DFT) 19 and in aqueous solution (PCM//DFT).…”

Applying vibrational spectroscopy to the study of nucleobases – adenine as a case-study

“…Regarding adenine (9H-purin-6-amine, C 5 H 5 N 5 ), work has been developed using Fourier transform infrared (FTIR) and Raman spectroscopic techniques aiming at elucidating its conformational preferences. [3][4][5][6][7][8][9] Fourteen different tautomeric species were found, both for the gas-phase and the aqueous solution, 10 comprising four amino and ten imino forms. In fact, adenine's tautomeric equilibrium has been studied in great detail and at different theoretical levels.…”

“…[3][4][5][6][7][8][9] Fourteen different tautomeric species were found, both for the gas-phase and the aqueous solution, 10 comprising four amino and ten imino forms. In fact, adenine's tautomeric equilibrium has been studied in great detail and at different theoretical levels.…”