. 2020 Mar 11;21(5):1920–1928. doi: 10.1021/acs.biomac.0c00057

Table 1. Molecular Weight and Functional Groups of the Lignin Fractions.

	EF₁	EF₂	SF
Mn (g/mol)^a	700	900	700
Mw (g/mol)^a	1050	1440	1120
PDI^a	1.5	1.6	1.6
aliphatic OH (mmol/g)^b	0.7	1.6	0.9
carboxylic acid (mmol/g)^b	0.3	0.4	0.7
noncondensed phenols (mmol/g)^b	1.2	1.1	3.1
C5-substituted phenols^c (mmol/g)^b	3.9	3.4	1.8
total phenols (mmol/g)^b	5.1	4.5	4.9

Estimated by SEC analysis.

Calculated by ³¹P NMR.

For EF1 and EF₂ the substitution at C5 mainly constitutes a methoxy group yielding sinapyl phenols (see Figure 1). For SF, the substitution constitutes a lignin moiety giving rise to so-called C5 condensed structures (e.g., phenolic 5–5′, 4-O-5′)