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15N NMR spectra of twelve neat ionic liquids derived from 1,3-disubstituted imidazolium salts were measured, and effects of nitrogen atoms substitution, type of anions and influence of solvents used for dilution of neat ionic liquids were studied. Changes in charge distribution are discussed.

The reaction between 5‐nitro‐2,1‐benzisothiazole‐3‐diazonium species and N‐substituted anilines produces the 1‐(5‐nitro‐2,1‐benzisothiazol‐3‐yl)‐3,3‐disubstituted triazenes 1. These triazenes are highly stable, and even in strongly acidic medium (0.5 mol⋅L−1 H2SO4) they are only slowly decomposed back to the diazonium ion and substituted anilinium ion (for the N‐ethyl derivative in 0.5 mol·L−1 H2SO4 at 25 °C, t1/2 ≈︁ 7 h). A series of six triazenes were characterised by their 1H and 13C NMR spectra and mass spectra. Two of the triazenes were also identified by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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The 17O NMR spectra of 17O isotope‐enriched 1,3,5‐trinitrobenzene and its Meisenheimer adducts with hydride ion (1), acetone anion (2) and methoxide ion (3) were measured. The adducts 1–3 show 17O signals shifted upfield compared with those of 1,3,5‐trinitrobenzene. A higher upfield shift is exhibited by the oxygen atoms of the 4‐nitro group (∼90 ppm) and a lower shift by those of the 2‐ and 6‐nitro groups (∼40 ppm). The shift is practically independent of the structure or bulkiness of the nucleophile bound at the tetrahedral centre C1 in the adduct and also, within an experimental error, of the counter ion and solvent (acetonitrile or a mixture of DMSO‐d6 and methanol). The measured δ(17O) values indicate that in the Meisenheimer adducts the negative charge at the oxygen atoms is larger in 4‐NO2 than in 2‐ and 6‐NO2 groups. Copyright © 2000 John Wiley & Sons, Ltd.