Figure 4.

Percentage of active C₁ (with free C₅) vs total furan content. The ratio obtained from HSQC is based on the furan ring ratio, whereas the initial ratio from Pyr-GC/MS is on a mass basis. In addition, a third ratio from the pyr-GC/MS data is included where the molecular mass of the fragments is used to normalize the masses. In short, on the sorting of pyr-GC/MS compounds: 2-(2-propenyl)-furan (active), furfural (active), 4-(2-furanyl)-3-buten-2-one (active), 5-HMF, and (2-furancarboxaldehyde, 5-methyl). For the HSQC integration, the carbons are measured as C₄ for the “active” furan by the signal at 7.28/106.38 ppm, whereas the signal at 7.53/122.86 ppm is integrated as C₄ for the second type of furan.