中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
4-硝基-2,1,3-苯并恶二唑1-氧化物 | 4-nitrobenzofuroxan | 18771-85-2 | C6H3N3O4 | 181.108 |
4-氯-7-硝基苯并-2-氧杂-1,3-二唑 | NBD chloride | 10199-89-0 | C6H2ClN3O3 | 199.553 |
The ionization of a series of 7-(4′-X anilino) 4-nitrobenzofurazans (4H) (X = NO2, CN, CO2Me, F, H, Me, OMe) to give the conjugate amide anions 4− has been studied by 1H and 13C NMR in Me2SO-d6. Concomitantly, their acidity (pKa) has been measured spectrophotometrically in a H2O–Me2SO mixture with a molar fraction [Formula: see text] Although the measured pKa values for the whole series of compounds 4H lie in a relatively narrow range (6.40, X = NO2/7.98, X = OMe), they reveal that each derivative is about 3 times more acidic than the similarly X-substituted 2,4,6-trinitrodiphenylamines. These results, together with an analysis of substituent effects on the proton and carbon chemical shifts [Formula: see text] and the related deprotonation parameters (Δδ), which are specially significant for H6, C4, C6, and C7, emphasize the very strong electron-withdrawing character of the 4-nitrobenzofurazanyl moiety. In addition, the observation of nice linear correlations of the type [Formula: see text] has enabled us to control and sometimes to firmly assign the various chemical shifts. Keywords: 7-anilino 4-nitrobenzofurazans, acidities, 1H and 13C NMR deprotonation shifts, water – dimethyl sulfoxide mixtures.