Complete NMR assignment and analysis of molecular structural changes of β–O–4 lignin oligomer model compounds in organic media with different water content
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Yuki Tokunaga
Abstract
The conformation of lignin in solvents is major key factors governing the physicochemical properties of aromatic polymers. However, the conformational changes of lignin in good and poor solvents is not clearly understood at the molecular level. In this study, short- (DP 2.77) and long-chain (DP 4.49) lignin oligomer model compounds composed solely of interunit β–O–4 bonds with a narrow polydispersity were synthesized, and their NMR spectra were recorded to evaluate the molecular structural changes induced by addition of water to an organic solvent. The spectral signals were completely assigned in DMSO-d6 and D2O by applying 2D 1H–13C HSQC, HMBC, and long-range heteronuclear single quantum multiple bond correlation (LR-HSQMBC). The conformation of the long- and short-chain lignin models were analyzed by 2D 1H–1H ROESY. In all the solvent systems, consisting of DMSO-d6 and containing 0–90% volume of acetic acid-d4 buffer in D2O (pD 5.0), the lignin models were found to have folded conformations, but more compact structures were observed in D2O compared with DMSO-d6.
Funding source: Japan Society for the Promotion of Science
Award Identifier / Grant number: Kakenhi JP18J20331
Funding source: Research Institute of Sustainable Humanosphere, Kyoto University
Award Identifier / Grant number: Collaboration program of RISH M2-2
Funding source: Institute of Advanced Energy, Kyoto University
Award Identifier / Grant number: Joint usage/Research Programs of IAE ZE30A-36, Z
Author contribution: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: This work was supported by JSPS KAKENHI grant number JP18J20331, a collaboration program of RISH (M2-2) and joint usage/research program of IAE (ZE30A-36, ZE31A-37).
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
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Supplementary material
The online version of this article offers supplementary material (https://doi.org/10.1515/hf-2020-0039).
© 2020 Walter de Gruyter GmbH, Berlin/Boston
Articles in the same Issue
- Frontmatter
- Original articles
- Heuristic study on the interaction between heat exchange and slow relaxation processes during wood moisture content changes
- Moisture content dependence of anisotropic vibrational properties of wood at quasi equilibrium: analytical review and multi-trajectories experiments
- Transient destabilisation in anisotropic vibrational properties of wood when changing humidity
- Rapid and nondestructive evaluation of hygroscopic behavior changes of thermally modified softwood and hardwood samples using near-infrared hyperspectral imaging (NIR-HSI)
- Density, hardness and strength properties of densified fir and aspen woods pretreated with water repellents
- Unraveling the natural durability of wood: revealing the impact of decay-influencing characteristics other than fungicidal components
- Complete NMR assignment and analysis of molecular structural changes of β–O–4 lignin oligomer model compounds in organic media with different water content
- Co-curing of epoxy resins with aminated lignins: insights into the role of lignin homo crosslinking during lignin amination on the elastic properties
- Facile fractionation of bamboo hydrolysate and characterization of isolated lignin and lignin-carbohydrate complexes
Articles in the same Issue
- Frontmatter
- Original articles
- Heuristic study on the interaction between heat exchange and slow relaxation processes during wood moisture content changes
- Moisture content dependence of anisotropic vibrational properties of wood at quasi equilibrium: analytical review and multi-trajectories experiments
- Transient destabilisation in anisotropic vibrational properties of wood when changing humidity
- Rapid and nondestructive evaluation of hygroscopic behavior changes of thermally modified softwood and hardwood samples using near-infrared hyperspectral imaging (NIR-HSI)
- Density, hardness and strength properties of densified fir and aspen woods pretreated with water repellents
- Unraveling the natural durability of wood: revealing the impact of decay-influencing characteristics other than fungicidal components
- Complete NMR assignment and analysis of molecular structural changes of β–O–4 lignin oligomer model compounds in organic media with different water content
- Co-curing of epoxy resins with aminated lignins: insights into the role of lignin homo crosslinking during lignin amination on the elastic properties
- Facile fractionation of bamboo hydrolysate and characterization of isolated lignin and lignin-carbohydrate complexes
