Reactivity of Lignin Diphenylmethane Model Dimers Under Alkaline Pulping Conditions

Revisiting the condensation reaction of lignin in alkaline pulping with quantitativity part I: the simplest condensation between vanillyl alcohol and creosol under soda cooking conditions

“…The obtained needle crystal was dissolved in acetone-d 6 with an aliquot of deuterium oxide, and then analyzed by 1 H-NMR, 13 C-NMR (JNM-A500, JEOL Ltd.), 13 C-NMR DEPT135, 2D-NMR 1 H-1 H COSY, 2D-NMR 1 H- 13 C HSQC, 2D-NMR 1 H- 13 C HMBC, and LC/MS (LC-2010C HT /LCMS-2020, Shimadzu Co., Kyoto, Japan). Conditions for the HPLC portion of the LC-2010C HT apparatus were as follows: an HPLC column, Luna 5 μm C18(2) 100 Å (length: 150 mm, inner diameter: 4.6 mm, particle size: 5.0 μm, Phenomenex, Inc., Torrance, CA, USA), was used at an oven temperature of 40 °C with a solvent flow rate of 0.2 mL/ min.…”

“…S1), 2D-NMR 1 H-1 H COSY (Additional file 1: Fig. S2), 2D-NMR 1 H- 13 C HSQC (Additional file 1: Figs. S3-S6), and 2D-NMR 1 H- 13 C HMBC spectra (Additional file 1: Figs.…”

“…S7-S11) are shown in the Additional file. The peaks appearing in the 1 H-NMR, 13 C-NMR, and MS spectra were assigned as below. In the following assignments, the letter 'Va-' or 'Cr-' indicates from which compound, Va or Cr, the targeted sites originated.…”

“…The condensation products were confirmed to be stable under alkaline conditions, using the α-5type product between vanillyl alcohol and creosol, 2-(4-hydroxy-3-methoxybenzyl)-6-methoxy-4-methylphenol, the α-1-type product between two molecules of vanillyl alcohol, bis(4-hydroxy-3-methoxyphenyl) methane, and the 5-CH 2 -5-type product between two molecules of creosol and HCHO, bis(2-hydroxy-3-methoxy-5-methylphenyl)methane [12,13].…”

Understanding the Nature and Reactivity of Residual Lignin for Improved Pulping and Bleaching Efficiency

“…As indicated in Figure 2.1, on mild alkali-O 2 treatments (0.5 M NaOH at 55°C), the cleavages of the α-5 (I) and 5,5'-type (II) DPM dimers all gave the alcohol-type products (vanillyl alcohol 1 or 5-hydroxymethylcreosol 2). Similar studies are extended to determine their reactivity under alkaline pulping conditions (35,38) and toward other nonchlorine bleaching agents including chlorine dioxide and alkali -peroxide, and a Lacaase-Mediator-System (LMS). The latter LMS was a new subtask.…”