SOME APPLICATIONS OF ULTRAHIGH-RESOLUTION N-15 NMR-SPECTROSCOPY

Ultrahigh resolution N-15 NMR spectra were measured for two nitroalkan es (MeNO2 1a, (BuNO2)-Bu-t 1c), two isocyanates ((BuNCO)-Bu-t 2c, Me3S iNCO 2d), four isothiocyanates (MeNCS 3a, EtNCS 3b, (BuNCS)-Bu-t 3c, M e3SiNCS 3d), one carbodiimide (Me3SiNCNSiMe3 4d), one keteneimine [Me3 SiNCC(SiMe3)(2) 5d], two sulphinyl imides ((BuNSO)-Bu-t 6c, Me3SiNSO 6 d), and N-tert-butyl-pyrrole 7c, in order to determine coupling consta nts J(N-15, C-13) and isotope induced chemical shifts (1) Delta(12/13) C(N-15) at the natural abundance of the isotopes. The values (1) Delta (12/13)C(N-15) can be separated into two groups, one dealing with NC s ingle and another one with NC double bonds. In each group (with few ex ceptions), the values (1) Delta(12/13)C(N-15) become more negative wit h a decrease in the absolute magnitude of \(1)J(N-15, C-13)\. The corr esponding values (1) Delta(14/15)N(C-13) show a similar behaviour. How ever, N-substituted pyrroles appear to be exceptional in this respect.