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Protonenresonanzspektren von Pteridinen (VI) . Mono‐ und Dikationen von 2‐Amino‐4‐oxo‐3, 4‐dihydropteridinen
Author(s) -
Dieffenbacher A.,
Philipsborn W.
Publication year - 1969
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19690520324
Subject(s) - chemistry , protonation , chemical shift , proton , proton nmr , nuclear magnetic resonance spectroscopy , nmr spectra database , spectral line , stereochemistry , ion , organic chemistry , physics , quantum mechanics , astronomy
Proton NMR. spectra of 18 pteridines have been measured in strongly acidic solutions. In trifluoroacidic acid mono‐cations are formed whereas in fluorosulfonic acid double protonation occurs. For the first time di‐cations of pteridines are described, and the structures of these species are determined by NMR. and UV. data. The chemical shifts of the NH 2 protons in the mono‐cations and of the methyl protons in the mono‐ and di‐cations follow linear correlations with the basic p K a values. From NMR. variable temperature measurements the energy barrier to internal rotation in the amidinium system has been ddtermined for both cations. The results are discussed with particular regard to the structure of the mono‐and di‐cations.