High resolution 13C NMR spectroscopy V—structure dependence of the 13C, H coupling constants in aceheptylene, azulene and 5-azaazulene

✍ Scribed by S. Braun; J. Kinkeldei; L. Walther

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: English
• Weight: 833 KB
• Volume: 14
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270140609

✦ Synopsis

Abstract

In order to study the structure dependence of the ^13^C,H coupling constants in polycyclic conjugated π electron systems with 5‐and 7‐membered rings, the ^1^H coupled ^13^C NMR spectra of aceheptylene, azulene and 5‐azaazulene have been analysed. The results are discussed, including published data of monocyclic reference compounds, and are compared to theoretical values calculated by the FPT‐INDO method. It is shown that, first, the geminal ^13^C,H couplings in the unsaturated 5‐membered carbocycles are predominantly dependent on CC bond lengths. Second, the vicinal ^13^C,H coupling constants in 5‐ as well as in 7‐membered unsaturated carbocyclic rings can be linearly related to the lengths of the central CC bonds. Third, the vicinal inter‐ring couplings show a large variation and give information on ring junction, thus being of special value in structure determination and are governed mainly by the bond angles. Fourth, the calculated ^13^C,H couplings across one and two bonds are totally useless for practical purposes; those across three bonds, however, at least reflect the experimental trends.