Nitrogen-15 Magnetic Resonance Spectroscopy. XV. Natural-Abundance Spectra. Chemical Shifts of Hydrazines

Abstract

The ^(15)N resonances of the methylhydrazines and some phenylhydrazines have been determined at the natural-abundance level of ^(15)N. The chemical shifts for the methyl compounds were interpretable in terms of deshielding α and β effects. The β shift, -24.4 ppm, is substantially larger than that found for amine ^(15)N (-18.2 ppm) or hydrocarbon nmr resonances (-9.7 ppm), and an explanation is offered in terms of possible steric influences. Although the ^(15)N shifts of the phenylhydrazines also change with structure, the data are so far insufficient to allow derivation of substituent parameters. Nonetheless, the effects of substitution appear to be less systematic than for the alkylhydrazines. The nmr chemical shifts of the methylhydrazines have been measured. While the shifts do not correlate with the ^(15)N shifts, they can be expressed in terms of deshielding β and shielding γ effects comparable to those found for hydrocarbons and alcohols.

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