Thermal behavior of beta-1 subunits in lignin: pyrolysis of 1,2-diarylpropane-1,3-diol-type lignin model compounds.
1,2-Diarylpropane-1,3-diol-type lignin model compounds, 1,2-bis(4-hydroxy-3-methoxyphenyl)propane-1,3-diol (1) and 1-(3,4-diethoxyphenyl)-2-(4-methoxyphenyl)propane-1,3-diol (2), were pyrolyzed at 500 degrees C for 4 s to clarify the thermal behavior of beta-1 subunits in lignin. Products were monitored by gas chromatography/mass spectrometry. The cleavage of the Calpha-Cbeta bond to produce benzaldehydes such as 4-hydroxy-3-methoxybenzaldehyde (9) and phenylethanals as the counterparts such as 4-hydroxy-3-methoxyphenylethanal (10) occurred in pyrolyses of both 1 and 2. In pyrolysis of 1, an oxetane pathway leading to the formation of Z/E-stilbenes without the gamma-CH2OH group such as Z/E-4,4'-dihydroxy-3,3'-dimethoxystilbene (3) was predominant. In pyrolysis of 2, the oxetane pathway was minor, while pathways producing a dimer with a =CgammaH2 group by loss of water and a dimer with an alpha-carbonyl group were predominant. Pyrolysis of Japanese cedar wood provided 3 and 10 in approximately 0.8% and 0.6% yields, respectively, based on the Klason lignin content, while pyrolysis of a guaiacyl bulk dehydrogenation polymer gave them in a very small amount.
Kuroda
Ken-Ichi
K
Department of Forest and Forest Products Sciences, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. kenfumi@agr.kyushu-u.ac.jp
Ashitani
Tatsuya
T
Fujita
Koki
K
Hattori
Takefumi
T
D032485:Cryptomeria / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D008031:Lignin / Q000737:chemistry*; D008956:Models, Chemical; D014934:Wood / Q000737:chemistry
D008031:Lignin