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)
MeO55.6/3.72C–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′)
-OCH356.5/3.18 The methyl in -methoxylated substructures ()
-OCH2CH364.0/3.35The methylene in -ethoxylated substructures (A′)
-OCH2CH2CH370.0/3.22the methylene in -propoxyed substructures (A′)
-OCH2CH2CH2CH368.0/3.28the 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)
S2,6103.8/6.62 in etherified syringyl units (S)
106.5/7.18 in oxidized syringyl units (S′)
G2111.0/6.95 in guaiacyl units (G)
G5115.0/6.72 in guaiacyl units (G)
G6118.8/6.72 in guaiacyl units (G)
I2109.5/7.10 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)