木材の重水素化赤外線吸収スペクトル

Abstract

木材の赤外スペクトルの帰属をするための一手段として, 木材およびその主化学的成分すなわちホロセルロース, ヘミセルロースおよびリグニンを重水素化しそれぞれの赤外スペクトルを測定した。それらを検討した結果, 次の事が明らかになった。1) 木材の赤外スペクトルで重水素化によって変化した個所は, 3340 (OH伸縮振動), 2510 (OD伸縮振動), 1650, 1450, 1370, 1110 (OH変角振動), 1060, 1040および810cm_-1であった。2) ヘミセルロースおよびリグニンを重水素化湿潤状態で測定した赤外スペクトルでは, 2510cm_-1の巾広い強いOD伸縮振動の吸収に加えて2790cm_-1に吸収を生じた。これはヘミセルロースおよびリグニンがともに湿潤状態ではそのOH基の一部は水素結合しないでフリーな状態で存在していることを示すものと推定される。

The deuterated infrared spectra were obtained from samples of wood sections, holocellulose, hemicellulose and milled wood lignin (MWL) of Japanese cypress (Chamaecyparis Obtusa Endl.) to make a much more complete band assignment. In the deuterated spectrum of wood sections, the absorption changes were found on the bands at 3340, 2510, 1650, 1450, 1370, 1110, 1060, 1040 and 810cm-1. (Fig. 1). The band at 3340cm-1., which was reduced in intensity on deuteration, is due to the OH stretching vibration. The bands at 1650, 1110 and 810cm-1. may arise partly from the OH deformation vibration because of the reduction of the intensity at the individual band on deuteration. The band at 2510cm-1. which appeared on deuteration is due to the OD stretching vibration and the bands at 1450 and 1370cm-1., which increased in intensity, may be assigned to the coupling band of the OD and other atomic groups. However it has not been possible to give a reasonable assignment to the other bands changed on deuteration. The effect of deuteration on the spectra of holocellulose, hemicellulose and MWL was confirmed (Figs. 2, 3 and 4). The infrared spectra of MWL in the region of 4000--2000cm-1. were measured both in the wet and dry states after deuteration (Fig. 4). The band at 2790cm-1. observed in the wet state probably arises from the OD stretching vibration of the OD groups which are not engaged in the hydrogen bond. Then this evidence suggets that there are a few free OH groups in MWL swollen with H2O.