Journal of the Chemical Society. Perkin Transactions 2 (2001) p. 1131 - 1138 (1996)
Update date:2022-07-31
Topics:
Castellan, Alain
Grelier, Stephane
Kessab, Larbi
Nourmamode, Aziz
Hannachi, Yacine
A lignin model molecule (DCOOH), incorporating an α-carbonyl guaiacyl part and a 4-hydroxy-3-methoxybenzyl alcohol moiety linked by an n-hexane chain, has been synthesized. The electronic absorption spectra in the ground and excited states (flash photolysis) and the luminescence properties in dilute solutions (alcohol and alkane) and in hydroxypropylcellulose (HPC) film were studied at room temperature and at 77 K in comparison with models representing the two ends. They show that in nonpolar and very good hydrogen donor solvents there is interaction between the excited carbonyl and the phenolic group, the chain probably being in a folded conformation. In alcoholic solvents and in HPC films, an intermolecular interaction between the carbonyl chromophore and the hydroxy group of the solvent was observed, the hexamethylene chain being in an extended conformation. UV irradiation of the dimer and the carbonyl monomer, incorporated in an HPC film, show similar reactivity which appears to involve an intermolecular hydrogen abstraction by the excited-state carbonyl group from the surrounding medium. The reactivity of the carbonyl derivatives in isopropyl alcohol and tetrahydrofuran (THF) was found to be similar to that observed for the films. In THF, two isomeric photoadducts between the carbonyl monomer (MCOET) and tetrahydrofuran were isolated and characterized. In alkane solvents, UV irradiation of the dimer leads to the appearance of a new band in the long wavelength range characteristic of the production and oxidation of phenoxyl radicals, which are oxidized to coloured structures such as quinones. The main conclusion of the study is that for the first time, it is shown that in the solid state the carbohydrate matrix does not tend to promote the oxidation process between the carbonyl and the phenol. This result is important for the understanding of the mechanism of photoyellowing of lignin-rich pulps.
View MoreXiamen Huasing Chemicals Co.Ltd.
Contact:0086-592-6228397
Address:NO.24, Xinglin North 2nd Road,Jimei district
Guangzhou Probig Fine Chemical Co., Ltd.
Contact:020-86297874
Address:No.2, 1/F, No.20, Hetai Road,Hebian Village, Baiyun District,Guangzhou,China
Contact:+86-518-81061113
Address:No. 8 Lingzhou Road, Lianyungang, Jiangsu, China
website:http://www.maisonchem.com.cn
Contact:0086-311-83833777
Address:Leitou industrial district, xinji, shijiazhuang city, hebei province,
Xi'an North Information Industry Co., Ltd. Weilv Chemical Department
Contact:+86-29-88156413
Address:Jixiang Road 99 Xi'an Shaanxi Province
Doi:10.1021/jo026643+
(2003)Doi:10.1002/anie.200503003
(2006)Doi:10.1021/jo0101712
(2001)Doi:10.1021/jo982387i
(1999)Doi:10.1039/b101668g
(2001)Doi:10.1039/P19720000380
(1972)
