Nuclear magnetic resonance studies on the configurations and conformations of heterocyclic nitrosamines

Abstract

The nuclear magnetic resonance spectra of various heterocyclic nitrosamines were studied in solution. A qualitative view of the long-range diamagnetic effects of a nitrosamino group is advanced and correlated with thechemical shifts of u-equatorial protons and the methyl group in those nitrosamines possessing a preferred conformation or a rigid system. The use of this correlation to decide the configuration a n d conformation of heterocyclic nitrosamines is discussed. A large chemical shift difference (ca. 3 p.p.rn.) between a cisu-axial and a ciscr-equatorial proton was noted.

Association of a Europium Shift Reagent with Dialkylnitrosamines

“…Previous4 workers (8)(9)(10) have shown the presence of E and Z isomers for an unsym4The Z-E nomenclature (20) is adapted to describe the geometric isomers and syn-utlli nomenclature is exclusively reserved to describe the locations of proton with respect to NNO orientation. Can.…”

“…2, this general trend of A, values suggests that the Eu atom is coordinated with the nitroso oxygen and not with the lone pair electrons of either nitrogen atom. In this connection, aromatic solvent shifts on nitrosamines have been proven to be just the opposite in every respect; the anti-protons are shielded more than the corresponding syn-protons (8)(9)(10).…”

“…7 and previous publications), we have been actively studying the stereochemistry of ground state nitrosamines (8,9). The n.m.r.…”

“…studies (8)(9)(10) have revealed that a nitrosamine molecule has a large charge separation, such as in structure 1, with the negative pole residing at the oxygen atom. The chemical shifts of nitrosamines have been interpreted satisfactorily by an approximation of the anisotropic effects of the NNO group (8). This structure (1) has been supported by various physical measurements (11,12).…”

Hydroacridines: Part 33. An experimental and DFT study of the 13C NMR chemical shifts of the nitrosamines derived from the six stereoisomers of tetradecahydroacridine

“…Owing to the various reaction capabilities of their functional group, nitrosamines became valued intermediates in syntheses of numerous organic compounds, and thus, their chemical, biochemical, photochemical, and physical properties are subject of continuing research efforts. Some of the most important advances in nitrosamines structural chemistry were achieved by workers using the methods of 1 H, 13 C, and 15 N NMR spectroscopy. The restricted rotation about the N─N bond in nitrosamines was documented and rationalized by the interaction between the electron lone pair of the amino nitrogen and the π electrons of the ─N═O group (n N ―π NO * conjugation) that confers a partial double‐bond character to these N─N bonds and a preference for a planar geometry (or very nearly so) to the amino nitrogens .…”