Research Article
Enhancement of Lignin Biopolymer Isolation from Hybrid Poplar by Organosolv Pretreatments
Table 2
Assignments of 13C–1H correlation signals in the 2D HSQC spectra of the alcohol lignin fractions from hybrid poplar.
| Labels | (ppm) | Assignment |
| | 53.5/3.07 | in resinol substructures (B) | | 53.0/3.48 | in phenylcoumaran substructures (C) | MeO | 55.6/3.72 | C–H in methoxyls | | 59.9/3.40 and 3.68 | in γ-hydroxylated substructures (A) | | 61.2/4.08 | in cinnamyl alcohol end-groups (F) | | 62.5/3.70 | in phenylcoumaran substructures (C) | | 71.0/3.80 and 4.15 | in resinol substructures (B) | | 71.6/4.82 | in substructures (A) | | 80.0/4.50 | in -methoxylated, ethoxylated, propoxyed and butoxyed substructures (A′) | -OCH3 | 56.5/3.18 | The methyl in -methoxylated substructures () | -OCH2CH3 | 64.0/3.35 | The methylene in -ethoxylated substructures (A′) | -OCH2CH2CH3 | 70.0/3.22 | the methylene in -propoxyed substructures (A′) | -OCH2CH2CH2CH3 | 68.0/3.28 | the methylene in -butoxyed substructures (A′) | (G) | 84.0/4.28 | in substructures (A) linked to a G unit | | 84.8/4.62 | in resinol substructures (B) | (S) | 85.8/4.12 | in substructures (A) linked to a S unit | | 86.8/5.45 | in phenylcoumaran substructures (C) | S2,6 | 103.8/6.62 | in etherified syringyl units (S) | | 106.5/7.18 | in oxidized syringyl units (S′) | G2 | 111.0/6.95 | in guaiacyl units (G) | G5 | 115.0/6.72 | in guaiacyl units (G) | G6 | 118.8/6.72 | in guaiacyl units (G) | I2 | 109.5/7.10 | in stilbenes units (I) | | 126.0/6.98 | in stilbenes units (I) | | 122.0/7.05 | in cinnamyl alcohol end-groups (F) | | 129.8/7.50 | in p-hydroxybenzoate substructures (PB) |
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