The title compound (2,4,5-trihydroxy-3-methylacetophenone, 1) was isolated as chromophore from aged cellulosic pulps. The peculiar feature of the compound is its weak aromatic system that can be converted into nonaromatic (quinoid or cyclic aliphatic) tautomers, depending on the conditions and reaction partners. In alkaline media, the participation of quinoid canonic forms weakens aromaticity, whereas in neutral and acidic media, the strong hydrogen bond between the 2-hydroxyl group and the acetyl moiety plays an important role in favoring quinoid tautomers. As a result, compound 1, with quinoid contributions being already “preset”, is relatively stable toward oxidation and hardly undergoes alkylation or nitration at CH-6, whereas the 2,4,5-trimethoxyderivative, being “properly” aromatic and even more sterically hindered, is readily alkylated or nitrated. The lability of the aromatic system is best demonstrated by the unusual reaction of 1 with hydroxylamine, producing a tetroxime that is derived from its 2,4,5-triketo tautomer. The high oxidative stability and low reactivity of the compound hinder oxidative bleaching of this chromophore in cellulosic pulps and detection reactions for analytical purposes.

中文翻译：

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2,4,5-三羟基-3-甲基苯乙酮：纤维素发色团作为芳香族的案例研究

从老化的纤维素纸浆中分离出作为发色团的标题化合物（2,4,5-三羟基-3-甲基苯乙酮，1）。该化合物的独特功能是其弱芳族体系，取决于条件和反应对象，该体系可转化为非芳族（醌或环状脂肪族）互变异构体。在碱性介质中，醌型典范形式的参与削弱了芳香性，而在中性和酸性介质中，2-羟基基团与乙酰基部分之间的强氢键在促进醌型互变异构体中起重要作用。结果，化合物1醌类化合物的作用已经“预设”，对氧化相对稳定，并且在CH-6处几乎不发生烷基化或硝化反应，而2,4,5-三甲氧基衍生物是“适当”芳族化合物，甚至在空间上受阻的，很容易被烷基化或硝化。芳香族体系的不稳定性最好通过1与羟胺的异常反应得到证明，该反应产生了由其2,4,5-三酮互变异构体衍生的四氧肟。该化合物的高氧化稳定性和低反应活性阻碍了该生色团在纤维素纸浆中的氧化漂白和用于分析目的的检测反应。