Table 2.
Quantitative evaluation of the impact of different structural descriptors (chemical substituents) on the reactivity of the guaiacyl OH group.
| Structural Descriptor | Compounds with and without the Indicated Chemical Feature * | Average ΔBDE of Phenolic OH Group between Compounds Bearing or not the Corresponding Chemical Substituent | Normalized Negative Impact of the Structural Descriptor, % | Normalized Positive Impact of the Structural Descriptor, % |
|---|---|---|---|---|
| α-CH2 | 2 (1) | −2.1 | - | 43 |
| α-CH2-CH3 | 3 (1) | −1.9 | - | 39 |
| α-CH2-CH2-CH3 | 4 (1) | −2.0 | - | 41 |
| α-C=C | 5(4), 13(14) | −2.3 | - | 47 |
| β-C=C | 6(4) | +0.6 | 12 | - |
| α-C=O | 7(2), 8 (3), 9(4), 12(10) | +4.8 | 98 | - |
| β-COOH | 10 (3), 12 (8) | +1.6 | 33 | - |
| γ-COOH | 14 (4) | +0.8 | 16 | - |
| α-OH | 11 (10) | +0.5 | 10 | - |
| α-O-4/β-5 | 15 (4) | +1.5 | 31 | - |
| β-O-4 ether linked | 18 (9), 19 (8) | +1.4 | 29 | - |
| biphenyl (5-5) | 16 (6), 17 (7) | −0.7 | - | 14 |
* model structures are depicted in Figure 1. Parent basic lignin structures are presented in parentheses.