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2,4,5-trihydroxy-3-methylacetophenone: A cellulosic chromophore as a case study of aromaticity

Formally Refereed
Authors: Nele Sophie Zwirchmayr, Thomas Elder, Markus Bacher, Andreas Hofinger-Horvath, Paul Kosma, Thomas Rosenau
Year: 2017
Type: Scientific Journal
Station: Southern Research Station
Source: ACS Omega


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.


Zwirchmayr, Nele Sophie; Elder, Thomas; Bacher, Markus; Hofinger-Horvath, Andreas; Kosma, Paul; Rosenau, Thomas. 2017. 2,4,5-trihydroxy-3-methylacetophenone: A cellulosic chromophore as a case study of aromaticity. ACS Omega. 2(11): 7929-7935.