One-scale basicities of diaminobenzenes and diaminonaphthalenes: from aniline to proton sponge

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• 作者：Marina P. Vlasenko and Valery A. Ozeryanskii
• 刊名：Journal of Physical Organic Chemistry
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：30
• 期：2
• 全文大小：5434K
• ISSN：1099-1395

文摘

Basicity constants, pK_a, for a wide range of mono-protonated diaminobenzenes and diaminonaphthalenes, including dimethylamino derivatives were for the first time uniformly measured in 20% aqueous ethanol (29 compounds) and 80% aqueous dioxane (39 compounds) spanning from aniline to 1,8-bis(dimethylamino)naphthalene (‘proton sponge’). The dioxane system proved to be more versatile and because of better solubility of N-alkylated polyaminoarenes allowed to add to the same scale some superbasic bis(dialkylamino)-, tetrakis(dialkylamino)-, and hexakis(dialkylamino)naphthalenes, thus extending the scale for almost 10 pK_a units, revealing possible limits of basicity changes in aromatic amines. The basicity of reference bases, pyridine and triethylamine, was also measured in these solvent systems. A group of N-alkylated compounds was found to be less basic in aqueous dioxane when compared with their NH₂-analogs. This anomaly was not observed in aqueous ethanol. Other basicity trends and correlations between different basicity scales were also discussed. Copyright