Identification of 5,5′-oxy-dimethylene-bis(2-furaldehyde) by thermal decomposition of 5-hydroxymethyl-2-furfuraldehyde

The thermal degradation of 5-hydroxymethyl-2-furfuraldehyde (5-HMF) was performed over a temperature range of 100–220°C in a stove during exposure periods of 15 min. The chromatographic analysis of the reaction mixtures was achieved by high performance liquid chromatography (HPLC)/diode array detection using a reversed-phase column Spherisorb ODS2, and the chromatograms recorded at 280 nm. Under the assayed conditions, apart from the peak of residual 5-HMF (RT 8.1 min), three major peaks corresponding to RT 14.5 min (compound 2), 20.9 (compound 3), 23.0 (compound 4) and a minor peak corresponding to 23.1 min (compound 5) were observed. Compound 2 was isolated by semipreparative HPLC and identified as 5,5′-oxy-dimethylene-bis(2-furaldehyde), a symmetric ether of 5-HMF (M+ 234; C12H10O5), by UV, 1H-NMR and GC–MS spectral analyses..