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- Title
An <sup>1</sup>H-NMR. Spectroscopic Study of Alloxazines and Isoalloxazines.
- Authors
Grande, Hans J.; Van Schagen, Cees G.; Jarbandhan, Tjan; Müller, Franz
- Abstract
1H-NMR.-spectra of a series of alloxazines and isoalloxazines and certain cationic derivatives were investigated (Tab. 2 and 5). Unequivocal assignment of all resonance signals was achieved in some compounds by selective deuteriation also by double resonance technique. The coupling constants were verified by computer simulation. Considerable enhancement of the signals due to H-C(9) and H-C(6) is found on decoupling of H3C-C(7), H3C-C(8) and H3C-N(10), resp. These results are compared with those obtained with FAD. The methyl resonance signal of the H3C-C(7) compounds give doublets due to coupling with H-C(6). The difference in chemical shifts observed upon successive formal introduction of methyl groups into the benzene nucleus of (iso)alloxazines indicates that the molecule becomes less planar thereby. The pyrimidine ring of (iso)alloxazines does not contribute to the ring current except by indirect effects via the carbonyl groups. The experimental data are compared with published MO calculations and discussed.
- Publication
Helvetica Chimica Acta, 1977, Vol 60, Issue 2, p348
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19770600207