The Modification of Lignin at Positions 2 and 6 of the Phenylpropanoid Nuclei. IV. The Reactivity of<i>Meta</i>Hydroxymethyl Groups

Klashorst, G. H. Van Der; Jackson, Siobhan A

doi:10.1080/02773818908050283

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“…Under alkaline conditions and temperatures ≥ 100 °C, free‐phenolic lignin can undergo hydrolysis of the β‐aryl ether and phenylcoumaran to give styryl ether and stilbene structures . Resorcinol has the capability to react with hydroxymethylated alkali lignin and lignin model compounds under acidic conditions to form methylenes between the C‐2‐ or C‐6 position on phenylpropanoids and the C‐4‐ or C‐6 position on resorcinol or to form various condensation products at the benzylic position on phenylpropanoids . However, since HMR is weakly basic (pH 8.5–9) and Acer spp.…”

Section: Resultsmentioning

confidence: 99%

Solution‐state NMR analysis of hydroxymethylated resorcinol cured in the presence of crude milled‐wood lignin from Acer saccharum

Yelle

2017

J of Applied Polymer Sci

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Resorcinol-formaldehyde adhesives can reinforce stress fractures that appear from wood surface preparation. Researchers have found that applying the resorcinol-formaldehyde prepolymer, hydroxymethylated resorcinol, to the surface of wood improves the bond strength of epoxy and polyurethane adhesives to wood. Hydroxymethylated resorcinol is thought to plasticize lignin components and stabilize stress fractures through reactions with lignin subunits and hemicelluloses in wood. In this study, a dilute solution of hydroxymethylated resorcinol (HMR) is cured in the presence of a crude milled-wood lignin (cMWL) from Acer saccharum and subsequently dissolved in dimethylsulfoxide-d 6 to delineate reactivity with lignin and O-acetyl-(4-O-methylglucurono)xylan using solution-state NMR spectroscopy. 1 H-13 C single-bond correlation NMR experiments revealed that the HMR only formed 4,4 0 -diarylmethane structures with itself in the presence of the cMWL; the 2-methylols that formed remained free and did not crosslink with resorcinol. Cured HMR resin formed both 4,4 0 -and 2,4-diarylmethane structures, confirming that the presence of lignin and O-acetyl-(4-O-methylglucurono)xylan hinders crosslinking at the C-2 position. No evidence of reactivity between HMR and lignin subunits was found. New peaks consistent with ester linkages were observed in 13 C-NMR spectra of the cMWL sample treated with HMR that may be attributable to HMR moieties condensing with glucuronic acid substituents.

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Section: Resultsmentioning

confidence: 99%

Solution‐state NMR analysis of hydroxymethylated resorcinol cured in the presence of crude milled‐wood lignin from Acer saccharum

Yelle

2017

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

The Modification of Lignin at Positions 2 and 6 of the Phenylpropanoid Nuclei. IV. The Reactivity ofMetaHydroxymethyl Groups

Cited by 1 publication

References 2 publications

Solution‐state NMR analysis of hydroxymethylated resorcinol cured in the presence of crude milled‐wood lignin from Acer saccharum

Solution‐state NMR analysis of hydroxymethylated resorcinol cured in the presence of crude milled‐wood lignin from Acer saccharum

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