Characteristic Coloration in Formation of N-1-Pyridinio Amidate and Enhancing Effect of Benzaldehydes.
作者:Mariko MORITA、Tetsuo NAGANO、Masaaki HIROBE
DOI:10.1248/cpb.41.2121
日期:——
N-Aminopyridinium iodide (NAPI) turned a bluish purple color upon the addition of NaOH. The NMR spectral data of the NAPI-NaOH system indicate that N-1-pyridinio amidate (NPA) is the species responsible for the coloration, which is probably due to intramolecular charge transfer transition. The intensity of the coloration increased remarkably with addition of benzaldehyde derivatives, especially p-nitrobenzaldehyde, to the NAPI-NaOH system. NAPI reacted with the benzaldehyde derivatives to form the corresponding Schiff bases. The mechanism of the coloration in the NAPI-NaOH-benzaldehyde derivative system is proposed to involve the formation of betaines, which can also be formed by adding NaOH to the isolated Schiff bases. Furthermore, there was a good correlation between the enhancing effects on the coloration and the redox potentials of the benzaldehyde derivatives. This indicates that benzaldehyde derivatives with an electron-withdrawing substituent group can enhance the coloration intensity much more effectively.
N-氨基吡啶碘化物 (NAPI) 在添加 NaOH 后变成蓝紫色。 NAPI-NaOH 体系的 NMR 光谱数据表明 N-1-吡啶酰胺化物 (NPA) 是导致着色的物质,这可能是由于分子内电荷转移跃迁所致。在 NAPI-NaOH 体系中添加苯甲醛衍生物,尤其是对硝基苯甲醛,显色强度显着增加。 NAPI与苯甲醛衍生物反应形成相应的席夫碱。 NAPI-NaOH-苯甲醛衍生物体系中的着色机制被认为涉及甜菜碱的形成,甜菜碱也可以通过向分离的席夫碱中添加NaOH来形成。此外,苯甲醛衍生物的着色增强效果与氧化还原电位之间存在良好的相关性。这表明带有吸电子取代基的苯甲醛衍生物可以更有效地增强显色强度。