Issue 6, 1981

Perfluoro effects in 15N nuclear magnetic resonance spectroscopy. Part 1. Aryl and N-heteroaryl azides

Abstract

15 N N.m.r. spectroscopic results are reported for a range of covalent azides RNαNβNγ(where R is perfluoroaryl, perfluoro- or chlorofluoro-pyridyl or -pyrimidinyl, or trimethylsilyl), and compared with literature values for related azides. The Nα and Nγ chemical shifts vary over a range of 80–100 p.p.m., and correlate with weak long-wavelength bands in the electronic spectrum that arise from magnetically active transitions (n→π* and π→π′*), the Nα,γ lines moving downfield as the bands move to lower energies. The Nβ chemical shift, however, varies rather little from its value in the azide anion. The Nα, γ chemical shifts are sensitive to the known inductive and conjugative influences of the R group. Perfluorination increases the shielding, by increasing the energy of the paramagnetic circulation; the perfluoro-effect diminishing with distance from the fluoro-substituent, and with the extent to which n→π* circulations are important in the deshielding. Thus the patterns of chemical shifts are explained by the relationships of the frontier orbitals for rotation of charge in the magnetic field.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1981, 975-979

Perfluoro effects in 15N nuclear magnetic resonance spectroscopy. Part 1. Aryl and N-heteroaryl azides

D. M. Kanjia, J. Mason, I. A. Stenhouse, R. E. Banks and N. D. Venayak, J. Chem. Soc., Perkin Trans. 2, 1981, 975 DOI: 10.1039/P29810000975

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements