Fig. 1: Schematic illustration of the conversion from fused benzene rings to benzene polycarboxylic acids (BPCAs) through nitric acid oxidation. | Nature Communications

Fig. 1: Schematic illustration of the conversion from fused benzene rings to benzene polycarboxylic acids (BPCAs) through nitric acid oxidation.

From: Polycyclic aromatics in the Chang’E 5 lunar soils

Fig. 1: Schematic illustration of the conversion from fused benzene rings to benzene polycarboxylic acids (BPCAs) through nitric acid oxidation.

During oxidation, a single fused benzene ring (highlighted in red) is preserved and substituted with carboxylic groups derived from adjacent carbon atoms. This process generates BPCAs with 2 to 6 carboxylic acid groups (highlighted in blue), including phthalic acid (1,2-B2CA), trimellitic and hemimellitic acids (1,2,4-B3CA and 1,2,3-B3CA), prehnitic, mellophanic and pyromellitic acids (1,2,3,4-B4CA, 1,2,3,5-B4CA and 1,2,4,5-B4CA), benzenepentacarboxylic acid (B5CA), and mellitic acid (B6CA)13. Additionally, di-nitrated 1,2-B2CA and mono-nitrated 1,2-B2CA, B3CA and B4CA are also produced15.

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