物理化学学报
物理化學學報
물이화학학보
ACTA PHYSICO-CHIMICA SINICA
2010年
1期
125-130
,共6页
陈晓华%樊永明%曹春昱%胡红智
陳曉華%樊永明%曹春昱%鬍紅智
진효화%번영명%조춘욱%호홍지
密度泛甬理论%醌型木素%含时密度泛函理论%光学特性%电子光谱
密度汎甬理論%醌型木素%含時密度汎函理論%光學特性%電子光譜
밀도범용이론%곤형목소%함시밀도범함이론%광학특성%전자광보
Density functional theory%Quinoid lignin%Time dependent density functional theoty%Optical characteristics%Electronic spectrum
为探索醌型木素化学结构与颜色的关系,以五种醌型木索模型物2-甲氧基-1,4-苯醌(I)、1,2-苯醌(Ⅱ)、4-亚烯丙基-2-甲氧基-2,5-环己二烯酮(亚甲基醌)(Ⅲ)、5-甲氧基-1,4-苯醌-2-氧负离子(Ⅳ)和5-甲基-1,4-苯醌-2-氧负离子(V)作为纸浆中醌型木素发色体的代表,在B3LYP/6-311++G(2d,p)水平上获得了它们在乙醇中的稳定基态构型,采用含时密度泛函理论(TD-DFT)在同等水平上计算了其在乙醇溶液中的电子光谱,并分析了它们在可见光范围内的吸收.结果发现:五种模型物在可见光范围内的吸收均源于电子的π→π~*跃迁,它们的最大吸收波长顺序依次为Ⅲ<Ⅰ<Ⅱ<Ⅳ<Ⅴ,吸光系数顺序依次为Ⅳ<Ⅰ<Ⅴ<Ⅱ<Ⅲ;漂白过程中生成的醌氧负离子以及邻醌类模型物具有中等大小的吸光系数(ε=1978-3197),吸收波长较长(445.47-552.36 nm),是漂白后纸浆具有颜色的重要原因.对醌类模型物吸收波长较小(414.91 nm),吸光系数大小为中等(ε=2094),亚甲基醌类模型物虽然吸光系数大(ε=31935),但吸收波长较小(407.90 nm),二者对漂白后纸浆的颜色影响较小.
為探索醌型木素化學結構與顏色的關繫,以五種醌型木索模型物2-甲氧基-1,4-苯醌(I)、1,2-苯醌(Ⅱ)、4-亞烯丙基-2-甲氧基-2,5-環己二烯酮(亞甲基醌)(Ⅲ)、5-甲氧基-1,4-苯醌-2-氧負離子(Ⅳ)和5-甲基-1,4-苯醌-2-氧負離子(V)作為紙漿中醌型木素髮色體的代錶,在B3LYP/6-311++G(2d,p)水平上穫得瞭它們在乙醇中的穩定基態構型,採用含時密度汎函理論(TD-DFT)在同等水平上計算瞭其在乙醇溶液中的電子光譜,併分析瞭它們在可見光範圍內的吸收.結果髮現:五種模型物在可見光範圍內的吸收均源于電子的π→π~*躍遷,它們的最大吸收波長順序依次為Ⅲ<Ⅰ<Ⅱ<Ⅳ<Ⅴ,吸光繫數順序依次為Ⅳ<Ⅰ<Ⅴ<Ⅱ<Ⅲ;漂白過程中生成的醌氧負離子以及鄰醌類模型物具有中等大小的吸光繫數(ε=1978-3197),吸收波長較長(445.47-552.36 nm),是漂白後紙漿具有顏色的重要原因.對醌類模型物吸收波長較小(414.91 nm),吸光繫數大小為中等(ε=2094),亞甲基醌類模型物雖然吸光繫數大(ε=31935),但吸收波長較小(407.90 nm),二者對漂白後紙漿的顏色影響較小.
위탐색곤형목소화학결구여안색적관계,이오충곤형목색모형물2-갑양기-1,4-분곤(I)、1,2-분곤(Ⅱ)、4-아희병기-2-갑양기-2,5-배기이희동(아갑기곤)(Ⅲ)、5-갑양기-1,4-분곤-2-양부리자(Ⅳ)화5-갑기-1,4-분곤-2-양부리자(V)작위지장중곤형목소발색체적대표,재B3LYP/6-311++G(2d,p)수평상획득료타문재을순중적은정기태구형,채용함시밀도범함이론(TD-DFT)재동등수평상계산료기재을순용액중적전자광보,병분석료타문재가견광범위내적흡수.결과발현:오충모형물재가견광범위내적흡수균원우전자적π→π~*약천,타문적최대흡수파장순서의차위Ⅲ<Ⅰ<Ⅱ<Ⅳ<Ⅴ,흡광계수순서의차위Ⅳ<Ⅰ<Ⅴ<Ⅱ<Ⅲ;표백과정중생성적곤양부리자이급린곤류모형물구유중등대소적흡광계수(ε=1978-3197),흡수파장교장(445.47-552.36 nm),시표백후지장구유안색적중요원인.대곤류모형물흡수파장교소(414.91 nm),흡광계수대소위중등(ε=2094),아갑기곤류모형물수연흡광계수대(ε=31935),단흡수파장교소(407.90 nm),이자대표백후지장적안색영향교소.
To explore the relationship between the structures and color of a quinoid lignin,quantum chemical calculations on five model lignin compounds:2-methoxy-1,4-benzoquinone (Ⅰ),1,2-benzoquinone (Ⅱ),4-acrol-2-methoxy-2,5-cyclohexadienone (p-quinone methide)(Ⅲ),5-methoxy-1,4-benzoquinone-2-oxygen anion(Ⅳ),5-methyl-l,4-benzoquinone-2-oxygen anion(Ⅴ)were performed using density functional theory at the B3LYP/6-311++G(2d,p)level.Optimized structures were obtained using ethanol as a solvent.Electronic spectra were produced using time dependent density functional theory(TD-DFT) at the same level.Results indicated that the maximum absorption band in the visible region of the five model compounds was caused by a π→π~* transition.The location of the maximum absorption band increased according to:Ⅲ<Ⅰ<Ⅱ<Ⅳ<Ⅴ.The oscillation strength at the maximum absorption band increased according to:Ⅳ<Ⅰ<Ⅴ<Ⅱ<Ⅲ.The quinone oxygen anion and the ο-quinone model compounds that were produced during the bleaching process had average extinction coefficients(ε=1978-3197)at 445.47-552.36 nm in the visible light region,which would be an important color sourog for pulp after bleaching.Although the P-quinone model compound-had an average extinction coefficient(ε=2094)and quinone methide had a large extinction coefficient(ε=31935),they did not have much effect on the color of the bleached pulp because of their comparatively short absorption wavelengths (414.91 and 407.90 nm,respectively).
