Reference

On the brightening of lignin by neutral hydrogen peroxide

On the brightening of lignin by neutral hydrogen peroxide. Oki, Tae; Ishikawa, Hisao; Okubo, Katsumi (Fac. Agric., Ehime Univ., Ehime, Japan). Kami Pa Gikyoshi, 32(6), 368-76 (Japanese) 1978. CODEN: KAGIAU. ISSN: 0021-5430. DOCUMENT TYPE: Journal CA Section: 43 (Cellulose, Lignin, Paper, and Other Wood Products) In the bleaching of hig-yield pulps with H2O2, the brightness of pulp increased with increasing time of treatment; the MWL [8068-00-6] and dioxane lignin [8068-03-9] content of pulp decreased with increasing content of H2O2. The absorbance of thiolignin [8068-10-8] and lignosulfonate (350 and 457 nm) also decreased during H2O2 treatment, indicating that lignin (I) in pulp was oxidatively degraded to H2O-sol. products. The chromophores in all I prepns. degraded more rapidly than the arom. nuclei. 2-Methoxy-p-benzoquinone [2880-58-2] and 2-methoxyhydroquinone [824-46-4] were important intermediates in the formation of colored substances during the reaction of vanillin [121-33-5] or acetovanillin [881-68-5] as I model compds. with H2O2. It was concluded that the leveling-off in brightness gain of pulps by H2O2 bleaching results from formation of new H2O2-resistant chromophores via p-quinone structures.

PMR spectra of lignin model compounds in alkaline solution

PMR spectra of lignin model compounds in alkaline solution. Yasuda, Seiichi; Yoon, Byung-Ho; Terashima, Noritsugu (Fac. Agric., Nagoya Univ., Nagoya, Japan). Mokuzai Gakkaishi, 24(3), 196-200 (Japanese) 1978. CODEN: MKZGA7. ISSN: 0021-4795. DOCUMENT TYPE: Journal CA Section: 43 (Cellulose, Lignin, Paper, and Other Wood Products) Section cross-reference(s): 22 The NMR shifts are reported for 24 lignin model compds. Based on spectral data for 4-hydroxy-3-methoxy-a-(2-methoxyphenoxy)acetophenone [22317-35-7] and 2-methoxy-4-methylphenol (I) [93-51-6], the ortho and meta substituent consts. of a ONa group on an arom. ring were 1.08 and 0.46, resp., in DMSO and 0. 22317-35-7 is the cas registry number of certain chemical which is used as reagents here.In this experiment, several chemicals are used like 22317-35-7 75 and 0.26, resp., in MeOH-H2O, indicating that the solvated phenoxide ion exists in I. In alk. soln., the proton of the formyl group of 4-hydroxy-3-methoxybenzaldehyde [121-33-5] and 4-hydroxy-3,5-dimethoxybenzaldehyde [134-96-3] as well as the proton of the acetyl group and the arom. proton at the C-5 position of 4-formyl-2-methoxyphenol acetate [881-68-5], 2-methoxy-4-[(2-methoxyphenoxymethyl)carbonyl]phenol acetate [66789-09-1], 4-formyl-2,6-dimethoxyphenol acetate [53669-33-3], 4-carboxy-2-methoxyphenol acetate [10543-12-1], 4-acetoxy-3-methoxycinnamic acid [2596-47-6] and 4-acetoxy-3-methoxy-a-(2-methoxyphenoxy)cinnamic acid [66789-10-4] shifted upfield. ..