## 2 Results and Discussion  
### Analysis of the Unmodified Lignin  
The structural alteration of the native lignin linkages can be seen from the HSQC spectrum of the MWL (Figure 1(a), pine, and 1(c), spruce) and BLN lignin (Figure 1(b), pine, and Figure 1(d), spruce), and the NMR shifts are listed in Table 1. Based on the integrals of the correlation peaks the small amount of remaining \(\beta\)-O-4 (A) (From MWL 27 to BLN 5% in pine and from 32 to 4% in spruce), \(\beta\)-\(\beta\) (B) (From MWL 7 to BLN 2% in pine and 5 to 3% in spruce), and \(\beta\)-5 (C) (From MWL 11 to BLN 3% in pine and 15 to 3% in spruce) only constitutes a small fraction compared to the MWL and no dibenzodioxocin (K), cinnamyl alcohol (E), cinnamyl aldehyde (I), or \(\gamma\)-substituted \(\beta\)-O-4 (A') could be detected in the BLN lignins. The aryl glycerol group (J) was formed during the process and is known to be formed during soda pulping [31; 32]; however, whether the group is formed during the initial PHWE or during the alkaline pulping was not confirmed. Both end ethers (L) and stilbenes (M) could be detected in the aromatic region and guaiacyl propanol (F), and secoisolariresinol (D) in the aliphatic region. Two overlapping signals B\({}_{\gamma^{\prime}}\) and J\({}_{\beta}\), marked by \({}^{*}\) in Figure 1(b),d, was detected from an unidentified structure. This was deduced as both B\({}_{\gamma^{\prime}}\) and J\({}_{\beta}\) show inconsistencies in their integrals from HSQC compared to B\({}_{\gamma}\) and Y\({}_{\alpha}\). The B\({}_{\gamma^{\prime}}\) which should be a CH\({}_{2}\) in the \(\beta\)-\(\beta\) resinol structure is a CH/CH\({}_{3}\) in both of the multiplicity edited HSQC lignin spectra, due to the overlapping of signals. From the aldehyde region (Figure 1(e),f) we detected the C\({}_{\gamma}\)-H from the cinnamyl aldehyde (I) moiety and a correlation peak originating from benzylic aldehyde (N) unit in the MWL (Figure 1(e)), but in the BLN lignin only the benzylic aldehyde (N) correlation peak remains (Figure 1(f)). There was an increase of carboxylic groups based on \({}^{31}\)P-NMR (Table 2), however, it seems that not all benzylic aldehydes were oxidized to carboxylic acids during the treatment and this could be due to the oxygen removal during the process. Only small amounts of carbohydrate impurities were detected in the HSQC spectrum of the BLN lignin. It is evident that significant condensation of the lignin occurred as the native lignin linkages were reduced in amount but the lignins retain a large molar mass. The lignins were also enriched with carbon compared to the MWL as seen from the elemental analysis (Table 3). Figure 2: Cont. Figure 2: Multiplicity edited HSQC of (**a**) Pine MWL; (**b**) Pine BLN lignin; (**c**) Spruce MWL; (**d**) Spruce BLN lignin; (**e**) aldehyde region of pine MWL; (**f**) aldehyde region of pine BLN and (**g**) the corresponding structures. (CH/CH\({}_{3}\) shown as positive (blue) and CH\({}_{2}\) as negative (red). The fragmentation and condensation can occur during the slightly acidic PHWE phase and/or during the alkali pulping, the mechanism can be either ionic and/or radical and will most likely occur at the C\({}_{\alpha}\), C\({}_{5}\), or C\({}_{6}\) position. The formation of condensed 5-substituted phenolic structures is seen from the \({}^{31}\)P-NMR spectrum as they are detected separately from the aliphatic and guaiacylic hydroxyl groups (see Supporting Data). The condensation was also seen from the HSQC of the methylated BLN lignin (Figure 3), where only the correlation peak of the methylated 4-OMe in 5-condensed structures was shifted to \(\delta_{\rm C}/\delta_{\rm H}\) (60.1/3.72) ppm (Figure 3b,c) and all other aromatic OMe-peaks will remain at approximately \(\delta_{\rm C}/\delta_{\rm H}\) (55.5/3.76) ppm.