木素的化学构造
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❖ The periodate method is based on the guaiacyl and syringyl structures with aqueous sodium periodate to o-quinone structures with the release of 1M methanol from each phenolic unit (Fig.4.27)
formation of methyl iodide when the sample
is treated with hydriodic acid at reflux temperature.
4
（二）羟基（hydroxyl group）
酚羟基（phenolic hydroxyl group）：存在于苯 环上；
脂肪族羟基（aliphatic hydroxyl group）：存在 于木素结构单元侧链上。
1.酚羟基 多数醚化，少数游离。
5
2.脂肪族羟基
6
使羟基甲基化的试剂
硫酸二甲酯
几乎全部游离羟基甲基化
重氮甲烷
游离的酸性酚羟基甲基化
可以测得游离羟基的含量 C9H7.68 (OCH3 )0.96 (PhOH)0.30 (AlOH)0.85 C9H7.68 (OCH3 )0.96 (OH)1.15 C9H7.68 (OCH3)0.96 (PhOH)0.30 (AlOH)0.85
❖ Chemical methods include determination of the increase in methoxyl content after reaction with diazomethane, selective deacetylation of acetylated lignin with aminolysis（氨基水解）, and determination of the amount of methanol formed after oxidation with sodium periodate
10
Fig. 4.27
11
How to analyze the phenolic hydroxyl groups (continued)?
❖ The aminolysis is based on the finding that phenolic acetates are cleaved with pyrrolidine(吡咯烷）much faster than aliphatic acetates. The pyrrolidine acetates formed in the reaction of an acetylated lignin is determined by GC (gas chromatography) (Fig.4.28)
示性式
C9H8.83O2.37(OCH3)0.96 C9H8.49O2.86(OCH3)1.43
C/H比例比较高，显示芳香族特性。
1
甲氧基是木素最重要的特征基团，其含量为： 针叶木木素：14％－16％ 阔叶木木素：19％－22％ 草本类木素：14％－15％
阔叶木木素中甲氧基含量比针叶木高,why? 木素中的甲氧基是联接在芳香环上的，而不 是联接在脂肪族侧链上。
12
Fig.4.28
13
How to analyze the aliphatic hydroxyl groups?
The total amount of hydroxyl groups in a lignin preparation can be determined by acetylation with acetic anhydride and pyridine followed by hydrolysis of the acetate and titration of the liberated acetic acid with a standard sodium hydroxide solution.The aliphatic hydroxyl content is determined by subtraction of the phenolichydroxyl content from the total hydroxyl content of the lignin.
一、木素的功能基
主要包括甲氧基（-OCH3）、羟基（-OH）和羰基（-CO）。 （一）元素组成及甲氧基（methoxyl group）
云杉和山毛榉MWL的元素分析值与甲氧基含量
木素 云杉MWL 山毛榉MWL
元素分析值/%
C
H
O
OCH3
64.77 6.39 28.58 16.13
60.58 6.23 33.19 21.46
9
How to analyze the phenolic hydroxyl groups?（continued）
❖ A more indirect method is based on permangnate oxidation after alkylation of the phenolic groups
7
-碳原子上的－OH
处于侧链上最活泼的部位，制浆பைடு நூலகம்化学反应中成为木素和制浆药液 的反应点
H
8
How to analyze the phenolic hydroxyl groups?
❖ Common instrumental methods for the estimation of phenolic groups in lignin are potentiometric and conductormeric titration, ionization difference UV spectroscopy, and NMR spectroscopy
2
甲氧基位置的确定
甲氧基所处的位置不同，裂开速度不同。
是连接在苯环上还是连接在脂肪族侧链上？
3
How to analyze the Methoxyl Groups?
The methoxyl content is a widely used for characterization of lignins. It gives a measure of their purity and of their plant origin. The method most widely used is based on the
formation of methyl iodide when the sample
is treated with hydriodic acid at reflux temperature.
4
（二）羟基（hydroxyl group）
酚羟基（phenolic hydroxyl group）：存在于苯 环上；
脂肪族羟基（aliphatic hydroxyl group）：存在 于木素结构单元侧链上。
1.酚羟基 多数醚化，少数游离。
5
2.脂肪族羟基
6
使羟基甲基化的试剂
硫酸二甲酯
几乎全部游离羟基甲基化
重氮甲烷
游离的酸性酚羟基甲基化
可以测得游离羟基的含量 C9H7.68 (OCH3 )0.96 (PhOH)0.30 (AlOH)0.85 C9H7.68 (OCH3 )0.96 (OH)1.15 C9H7.68 (OCH3)0.96 (PhOH)0.30 (AlOH)0.85
❖ Chemical methods include determination of the increase in methoxyl content after reaction with diazomethane, selective deacetylation of acetylated lignin with aminolysis（氨基水解）, and determination of the amount of methanol formed after oxidation with sodium periodate
10
Fig. 4.27
11
How to analyze the phenolic hydroxyl groups (continued)?
❖ The aminolysis is based on the finding that phenolic acetates are cleaved with pyrrolidine(吡咯烷）much faster than aliphatic acetates. The pyrrolidine acetates formed in the reaction of an acetylated lignin is determined by GC (gas chromatography) (Fig.4.28)
示性式
C9H8.83O2.37(OCH3)0.96 C9H8.49O2.86(OCH3)1.43
C/H比例比较高，显示芳香族特性。
1
甲氧基是木素最重要的特征基团，其含量为： 针叶木木素：14％－16％ 阔叶木木素：19％－22％ 草本类木素：14％－15％
阔叶木木素中甲氧基含量比针叶木高,why? 木素中的甲氧基是联接在芳香环上的，而不 是联接在脂肪族侧链上。
12
Fig.4.28
13
How to analyze the aliphatic hydroxyl groups?
The total amount of hydroxyl groups in a lignin preparation can be determined by acetylation with acetic anhydride and pyridine followed by hydrolysis of the acetate and titration of the liberated acetic acid with a standard sodium hydroxide solution.The aliphatic hydroxyl content is determined by subtraction of the phenolichydroxyl content from the total hydroxyl content of the lignin.
一、木素的功能基
主要包括甲氧基（-OCH3）、羟基（-OH）和羰基（-CO）。 （一）元素组成及甲氧基（methoxyl group）
云杉和山毛榉MWL的元素分析值与甲氧基含量
木素 云杉MWL 山毛榉MWL
元素分析值/%
C
H
O
OCH3
64.77 6.39 28.58 16.13
60.58 6.23 33.19 21.46
9
How to analyze the phenolic hydroxyl groups?（continued）
❖ A more indirect method is based on permangnate oxidation after alkylation of the phenolic groups
7
-碳原子上的－OH
处于侧链上最活泼的部位，制浆பைடு நூலகம்化学反应中成为木素和制浆药液 的反应点
H
8
How to analyze the phenolic hydroxyl groups?
❖ Common instrumental methods for the estimation of phenolic groups in lignin are potentiometric and conductormeric titration, ionization difference UV spectroscopy, and NMR spectroscopy
2
甲氧基位置的确定
甲氧基所处的位置不同，裂开速度不同。
是连接在苯环上还是连接在脂肪族侧链上？
3
How to analyze the Methoxyl Groups?
The methoxyl content is a widely used for characterization of lignins. It gives a measure of their purity and of their plant origin. The method most widely used is based on the