yqChapter 22 Carbohydrates-2

Numbering of Aldoses
Carbons in monosaccharides are numbered such that the C=O group has lowest number:
H O C 1 2 CHOH 3 CHOH 4 CHOH 5 CHOH 6 CH2OH Aldohexoses
Aldose Aldotetrose Aldopentose Aldohexose Aldoheptose Aldooctose
Containing a aldehyde group
Ketose Ketotetrose Ketopentose Ketohexose Ketoheptose Ketooctose
H C HO
O H CH2OH
D、L只表示 构型，与旋 光方向无关
(+)-D-Glyceraldehyde
(-)-L-Glyceraldehyde
Fisher Projections of Carbohydrates
相对构型：
H HO H H CHO OH H OH OH CH2OH CH2OH O HO H H OH H OH CH2OH D-(-)-果糖
CHO HO H CH2OH L-(-)-甘油醛
CHO H OH CH2OH D-(+)-甘油醛
D-(+)-葡萄糖
编号最大的手性碳的构型与D-(+)-甘油醛相同——D构型
与L-(-)-甘油醛相同——L构型
Epimers
Epimers (差向异构体 ) ——Distereomers that differ in configuration at only one chirality center are called epimers
H C H O 1 C 2 CHOH 3 CHOH 4 CH2OH Aldotetroses
O
H O 1 C 2 CHOH 3 CH OH 2 Aldotrioses
1 2 CHOH 3 CHOH 4 CHOH 5 CH2OH Aldopentoses
Numbering of Ketoses
Carbons in monosaccharides are numbered such that the C=O group has lowest number:
Monosaccharides
•Monosaccarides are the simplest carbohydrates is not cleaved to a simpler carbohydrate on hydrolysis. •Glucose, for example, is a monosaccharide.
CH2OH O CH2OH O CHOH n CH2OH Ketose HO H H H OH OH CH2OH Ketose (open chain form) HO OH Ketose (cyclic form) O OH OH OH
1 1 2 CH2OH O 2
CH2OH O
1 CH2OH 2 O
CHO H R OH
Glyceraldehyde:The Simplest Carbohydrate
120°
H O H H H OH OH HO OH C O
H
H
O C
H C H
O OH CH2OH
OH
CH2OH
R-(+)-Glyceraldehyde
D-Glyceraldehyde
H C H
O OH CH2OH
OH OH CH2OH
CHO OH OH OH CH2OH D-(-)-arabinose D-(-)-ribose HO
CHO OH OH CH2OH
CHO OH 5C HO OH CH2OH D-(+)-xylose HO HO D-(+)-lyxose
CHO
OH CH2OH
CHO OH HO OH OH OH CH2OH
Carbohydrates Form Cyclic Hemiacetals
HO
1 CHO
O OH OH
H H
2
OH OH
H H
4
H H O H
D-(-)-idose
CHO OH HO HO OH CH2OH
D-(+)-galactose
CHO HO HO HO OH CH2OH
D-(+)-talose
6C
天然存在的单糖大多是D型的。
Monosaccharides
Structures
糖一般使用俗名，并常用Fischer投影式表示糖的结构，采用 D- 和 L- 表示构型异构
mirror
1
CHO H H
CHO OH CH2OH
D-glyceraldehyde
1 2
CH2OH C O
HO
2 3
CH2OH
3
CH2OH
L-glyceraldehyde
dihydwk.baidu.comoxyacetone
L-甘油醛
FischerD-甘油醛 formulas 二羟基丙酮 projection
D —— 相距醛（酮）基最远的手性碳上的羟基处在右边; L —— 相距醛（酮）基最远的手性碳上的羟基处在左边
Classifications
Carbohydrates
Oligosaccharide Disaccharide other Monosaccharide Polysaccharide
Starch Cellulose other
aldose 醛糖
ketose 酮糖
triose tetrose pentose hexose 丙糖 丁糖 戊糖 己糖
含多个手性中心的旋光异构体中，那些只有一个手性中心的 构型相反的异构体。
Mutarotation
变旋现象
从<50℃的水中结晶 得到的葡萄糖
[α]
从>98℃的水中结晶 得到的葡萄糖
m.p. 146 ℃
+112o +52.7o
m.p. 150 ℃
+18.7o
Mutarotation
实验事实：葡萄糖（醛糖）
3 CHOH 4 CHOH 5 CHOH 6 CH2OH Ketohexoses
1 CH2OH 2 O 3 CH OH 2 Ketotrioses
3 CHOH 4 CHOH 5 CH2OH Ketopentoses
3 CHOH 4 CH2OH Ketotetroses
Fisher Projections of Carbohydrates
Basic Carbohydrate Nomenclature
O O Monosaccaride O O Disaccaride
• Monosaccharide
• Disaccharide • Oligosaccharide
• Polysaccharide
O
O
O O O
O Oligosaccarides (1-5) Polysaccharide (>5) n
Introduction
Carbohydrates
Originally, compounds such as aldoses and ketoses, having the stoichiometric formula Cn(H2O)n, hence ‘hydrates of carbon’. The generic term carbohydrate includes monosaccharides, oligosaccharides and polysaccharides as well as substances derived from monosaccharides through various transformations.
Cn(H2O)n ….. a hydrate of carbon?
Perhaps, but more accurately described as polyhydroxy aldehydes and ketones or substance that yield such compounds on hydrolysis. Other names —— Saccharide, Sugar 糖－多羟基醛或多羟基酮以及它们的聚合物
Containing a keto group
The Family of D-aldoses
CHO 4C
CHO
3C
OH CH2OH
D-(+)-Glyceraldehyde (absolute configuration)
CHO D-(-)-erythrose D-(-)-threose HO OH CH2OH
In the Fischer convention, the carbon chain is in vertical arrangement with the carbonyl group at the top (for aldoses), or nearest to the top (for ketoses). The horizontal bonds (CH and C-O) project towards viewer. These projections represent stereochemistry not conformation.
基本内容和重点要求
单糖的结构。单糖的开链式结构及其费 歇尔投影式，哈沃斯式及其构象表达式。 单糖的化学性质。氧化、还原反应；成 苷、成脎反应；互变异构及变旋光现象。 重要的单糖、二糖和多糖的结构特征。
重点要求掌握单糖(葡萄糖、果糖)的开链式、 氧环式的费歇尔投影式、哈沃斯式和构象式；单糖 的变旋光现象；单糖和二糖的化学性质。
在同一分子中含有羟基和羰基是糖的基本结构特征， 这是糖的物理性质以及化学性质的结构基础
Monosaccharides
Monosaccharides are Defined According to Chain Length and Type of Carbonyl Group
•No. of carbons • 4 • 5 • 6 • 7 • 8
①＋ HCN ②银镜反应
(可以和Fehling,Tollen试剂反应)
醛所特有的反应
不能生成NaHSO3加成物
品红试验不变色
IR无 ν
C＝O
吸收
无醛 的反应
O C H H C OR OR
NMR 无 O＝C－H 信号 只能与一分子的醇作用
+ 2ROH
Mutarotation
CH2OH O OH OH OH α-D-葡萄糖 36.4％ H CH3OH CH2OH O OH OH OH α-苷 β-苷
+
OH
H HO H H
CHO OH H OH OH CH2OH < 0.01 %
CH2OH O OH OH OH OH β-D-葡萄糖 63.6％ H CH3OH
An additional asymmertric carbon atom.
CH2OH O OCH3 OH OCH3 OH OH
Actually pentoses and hexoses exist in solution as intramolecular hemiacetals or hemiketals, forming stable 5 or 6 membered rings (furan and pyran ring).
D-(+)-allose
CHO OH OH OH CH2OH
D-(+)-alrose
CHO OH HO HO OH OH CH2OH
D-(+)-glucose
CHO HO OH OH CH2OH
D-(+)-mannose
CHO OH HO OH HO OH CH2OH
D-(-)-gulose
CHO OH HO OH CH2OH
HO OH HO H OH OH HO OH D-Glucose (open chain form) D-Glucose (cyclic form in Mills projection) OH HO OH D-Glucose (cyclic form in Haworth projection) OH O HO O OH HO O OH
Chapter 22 Carbohydrates
C and O Cycle in Nature Photosynthesis
Capture the Sun's Energy
CO2 + H2O Respiration
Carbohydrates + O2
Release the Chemical Energy