第五章 芳香烃 aromatic compounds
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第五章 芳香烃 Aromatic compounds. 概述. 1. 脂肪烃及芳香烃. Aliphatic and aromatic compounds 芳香性 Aromaticity. KMnO 4. ×. +Br 2 /CCl 4. ?. ×. +Br 2 / FeBr 3. Aromaticity 芳香性 稳定的环,易取代,难加成,难氧化. 2. 烷基苯工业来源( Industrial source of alkylbenzenes ). Coal Petroleum (见书 第四节 ). Coke( 焦炭). △ ( no air). - PowerPoint PPT PresentationTRANSCRIPT
第五章 芳香烃 Aromatic compounds
CHCOHCH3CHCH2
CH3
CH3O
F
CHCOOH
CH3
NH
CH2COONa
Cl Cl
OCCH3
COOH
O
Ibuprofen
Flurbiprofen Aspirin
Diclofenac Sodium
概述
1. 脂肪烃及芳香烃
Aliphatic and aromatic compounds
芳香性 Aromaticity
Br
+Br2/CCl4
×
+Br2/ FeBr3
×KMnO4
Aromaticity 芳香性稳定的环,易取代,难加成,难氧化
?
2. 烷基苯工业来源( Industrial source of alkylbenzenes )
CoalPetroleum(见书第四节)
•Coal△ ( no air)
Coke( 焦炭)
•Coal tar( 煤焦油 )+ Coal gas
Benzene,toluene,xylenes,phenol
cycloalkanes Aromatic hydrocarbonCatalytic reforming催化重整
馏分名称 沸点范围 / ℃ 主要成分
轻油 <180 苯、甲苯、二甲苯
酚油 180~210 苯酚、甲苯酚等
萘油 210~230 萘、甲基萘等
洗油 230~300 联苯、苊、芴等
蒽油 300~360 蒽、菲等
沥青 >360 沥青、游离碳
煤焦油的分馏产物煤焦油的分馏产物
3. 分类 单环芳烃 多环芳烃 非苯芳烃
第一节 单环芳烃 苯及同系物( benzene and homolog )
一 . 苯的结构 ( structure of benzene ) 1. 开库勒结构式( Kekule structur
e ) In 1825 M.Faraday In 1834 E.Mitscherlich In 1865 August Kekule
August Kekule I was sitting writing at my textbook,but t
he work did not progress;my thoughts were elsewhere. I turned my chair to the fire,and dozed.Again the atoms were gamboling before my eyes.This time the smaller groups kept modestly in the beckground.My mental eye,rendered more acute by repeated visions of this
kind,could now distinguish larger structures of manifold conformations;long rows,sometimes more closely fitted together;all twisting and turning in snake-like motion.But look!What was that?One of the snakes had seized hold of its own tail,and the form whirled mockingly before my eyes.As if by a flash of lightning I woke;……I spent the rest of the night working out the consequences of the hypothesis. Let us learn to dream,gentlemen,and then perhaps we shall learn the truth.
August Kekule
苯环结构的诞生是有机化学发展史上的一块里程碑
Kekule formula
H
HH
H
H
H
Br
Br
Br
Br
Dewar formula
2. 轨道理论 Theory of orbit
C —SP2
( 1 ) C sp2 hybridized
( 2 ) Particularly stable
( 3 )电子离域 Electron Delocalization
CH3—CH3 Csp3-Csp3 154 pm
CH2=CH—CH3 Csp2-Csp3 150 pm
CH2=CH—CH=CH2 Csp2-Csp2 146 pm
C6H6 Csp2-Csp2 139 pm
3. 分子轨道理论Theory of molecular orbit
4. 共振( Resonance structure of benzene )
Resonance Contributors
+
+
Linus pauling
电子离域与共振Electron Delocalization and Resonance
上述非经典结构式较好地表示了电子的离域,但是却无法告诉我们该结构中含有多少双键。因此化学家常用共振结构(共振极限结构)来表示。
p-electrons in conjugated dienes and benzene are delocalized 定域电子:被限制在两个原子核区域内运动的电子 离域电子:不局限于两个原子核区域内运动的电子 这种电子的离域作用我们也称之为共轭作用
H2CHC
HC CH2
How to drow resonance contributors
Rules for Drawing Resonance Contributors Only electrons move. The nuclei of the atoms
never move The only electrons that can move are π
electrons and nonbonding electrons The total number of electrons in the molecule
does not change, neither do the numbers of paired and unpaired electrons
In order to draw contributors, the electrons in one resonance contributor are moved to generate the next contributor.
The electrons can be moved in one of the following ways
( 1 ) Move πelectrons toward a positive charge
CH2 CH2 CH2
CH2 CH2
CH2
+
+
+
+
( 2 ) Move πelectrons toward a π bond
( 3) Move a nonbonding pair of electrons toward a πbond
( 4) Move a single nonbonding electron toward a πbond
CH2CH2
CH2 CH2
CH2
1 2 3
4 5
CH2
共振杂化体比它的任何一个共振式都要稳定 共价键数目越多的共振式越稳定 共振式中的电荷越分散就越稳定 越稳定的共振式对共振杂化体的贡献越大
CHH2C CH CH2 CH2 CH CH CH2
CH2 CH CH CH2CH2 CH CH CH2
CHH2C CH CH2 CHH2C CH CH2
CH2CH2 CH CH
1, 3-butadiene
( 5)相对稳定的共振式的数目越多,共振杂化体越稳定
( 6 )共振式越接近等价,共振杂化体越稳定
二 . 命名 Nomenclature
•1. 简单•×× 苯 ( ×× benzene )
Cl NO2
Chlorobenzene Nitrobenzene
Special names
CH3NH2
Toluene Aniline
2. 相对复杂
CH=CH2
CH3CHCH2CH2CH3
2- 苯基戊烷2 - phenylpentane
苯乙烯Styrenephenylethylene
3. 多取代基
CH3
CH3
CH3
CH3
CH3
CH3
O-Dibromobenzene
orthom-Dibromobenzene
metap-Dibromobenzene
para
Cl
SO3H
NO2
2- 氯 -3- 硝基苯磺酸2-chloro-3-nitrobenzene-sulfonicacid
优先次序:
-COOH , -SO3H , -CN , -CHO ,>C=O , -OH , -NH2 , -R , - X , NO2
三、物理性质 苯:无色透明 , 易燃液体。 不溶于水。遇热、明火易燃烧、爆炸。 能与氧化剂 , 发生剧烈反应。 蜡、树脂、油的溶剂 ; 合成化学制品和制药的中间体。汽油一种成份 ,含量 <2%
急性苯中毒:麻醉作用 慢性中毒
四、化学性质
(一)芳香亲电取代反应 ( electrophilic aromatic substitution reactions )
Br+Br2/ FeBr3
H E+ E¡ª¡ª Nu
¦Ä ¦Ä+ - + H¡ª¡ª Nu
Step 1:
H
E
H
EH
E
H
++
+
E ++
E
HE
+Nu + H-Nu
Step 2:
:
机理 Mechanism:
Step 1:
Reaction coordinate diagrams:
Br
+ Br2
FeBr3
+ HBr»òFe·Û
1. 卤代 Halogenation
Catalyst:FeCl3, AlCl3, CuCl2, SbCl5
Bromobenzene
FeBr3 + Br2 → FeBr4- + Br+
diazepam
N
N
Cl
OCH3
+
NO2
+ H2OH2SO4
50~60¡æ
ŨHNO3
2. 硝化 Nitration
NO2NO2
NO2
H2SO4+ £¨·¢ÑÌ£©HNO395 ¡æ
£¨·¢ÑÌ£©
Nitrobenzene
H
H
HO¡ª NO2 HOSO3H HSO4
_ H¡ª O¡ª NO2
+
H¡ª O¡ª NO2
+H2SO4
NO2+
H3O+
HSO4
_+
+ +
+ +
硝基苯 硝基苯 ; 密斑油 ; 苦杏仁油 相对密度 1.205 。难溶于水 硝基苯的主要毒作用
3. 磺化 Sulfonation
—— reversible reaction
SO3H
SO3H
H2SO4H2O
H2SO4 SO3 H2SO4
ÊÒΡ¤
+
+
+
+
苯磺酸 Benzenesulfonic acid
SO3H
SO2Cl
ClSO3H HCl
2ClSO3H
+
+
+
SO2NH2
NH2 sulfanilimide
NH2 N=N
NH2
SO2NH2
prontosil
磺胺甲噁唑( sulfamethoxazole , sinomin , SMZ )又名新诺明
NH2 SO2NH
NO CH3
N
ON
O
噁唑 异噁唑
4. 傅 - 克烷基化反应 (Friedel-Crafts Alkylation )
傅瑞尔-克拉夫茨 C . Friedel 1832-1899 J.A.Crafts 1839-1917
Note:
①催化剂 Catalyst:Lewis acids, AlCl3, FeCl3, ZnCl2, SnCl4, BF3
② 重排 Rearrangement may occur in alkylation
10
10
③多元取代物 polysubstitution——Limitation
+ÎÞË®AlCl3
CH3Cl
CH3
ÎÞË®AlCl3
CH3H3C
④Aromatic rings containingthe
group do not undergo F-C Alkylation
NO2 ¡¢ COOH ¡¢ SO3H ¡¢ C
O
R ¡¢ CN ¡¢
NH2 ¡¢ NHR ¡¢ NR2
⑤polyhalogenated alkanes ?
ÎÞË®AlCl3+ CH2
C
CH2 CH2
C
CH2 CH2 CH2
ÎÞË®AlCl3CH2CH2CH2
Cl
+ (CH3)2CHOHH2SO4
65¡æ
CH(CH3)2
+H2SO4
CH
CH2CH3CH3CH2CH=CH2
CH3
⑥alcohol,alkene
5. 傅 - 克酰基化反应 (Friedel-Crafts Acylation )
R C ClO
+ AlCl3: R C O: R C O:- AlCl4
acylium ion没有重排问题
+ CH3CH2COClAlCl3
O
Zn-Hg
ŨHCl
5 个亲电取代反应
H
NO2 SO3HR
O
R
Cl Br
Nitration
HalogenationF-C acylation
F-C alkylation Sulfonation
亲电试剂 electrophile : —— Cl-Cl+ - -AlCl3
—— Br-Br+ - -FeBr3
—— +NO2 (obtained by HNO3 + H2SO4)
—— +SO3H (from H2SO4) or SO3
—— R+ (obtained by R-Cl + AlCl3)
—— RC+=O (obtained by RCOCl + AlCl3)
思考题:如何从苯合成正丁基苯?