File

Some history ,[object Object],[object Object],[object Object],[object Object]

בנזן - נוסחה אמפירית C 6 H 6 דוגמה לנוסחה אמפירית כזו בה היחס בין הפחמן למימן הוא 1:1 היא זו של האצטילן - C 2 H 2 HC=CH שוני גדול בין השניים - בניגוד לאצטילן בנזן לא מגיב ל : HCl, KMnO 4 , Br 2 , H 2 O/acid , אינו עובר תגובות של סיפוח שראינו באלקנים .

Kekul י and the Structure of Benzene

[object Object],Kekul י Formulation of Benzene H H H H H H

[object Object],Kekul י Formulation of Benzene H H H H H H H H H H H H

[object Object],Kekul י Formulation of Benzene H X X H H H H X X H H H

[object Object],Structure of Benzene Benzene has the shape of a regular hexagon.

All C—C bond distances = 140 pm 140 pm 140 pm 140 pm 140 pm 140 pm 140 pm

All C—C bond distances = 140 pm ,[object Object],140 pm 140 pm 140 pm 140 pm 140 pm 140 pm 146 pm 134 pm

The Stability of Benzene ,[object Object],[object Object]

[object Object],Thermochemical Measures of Stability  H°= – 208 kJ + 3H 2 Pt

Figure 11.2 (p 404) ,[object Object],120 kJ/mol 360 kJ/mol 3 x cyclohexene

Figure 11.2 (p 404) ,[object Object],[object Object],208 kJ/mol 360 kJ/mol 3 x cyclohexene

אנטלפית השריפה של בנזן חום השריפה מחושב - Kcal/mol -827 חום השריפה שמתקבל בפועל - 789 Kcal/mol - הפרש של 38 ק”קל למול

A Resonance Picture of Bonding in Benzene

[object Object],Resonance Formulation of Benzene H H H H H H H H H H H H

[object Object],Resonance Formulation of Benzene

Orbital Hybridization Model of Bonding in Benzene ,[object Object],Figure 11.3

Orbital Hybridization Model of Bonding in Benzene ,[object Object],[object Object],Figure 11.3

מושג הארומטיות ,[object Object],[object Object],[object Object],[object Object],[object Object]

תרכובות ארומטיות

Examples of Aromatic Hydrocarbons Benzene Toluene Naphthalene H H H H H H CH 3 H H H H H H H H H H H H H

11.8 Polycyclic Aromatic Hydrocarbons

[object Object],Naphthalene most stable Lewis structure; both rings correspond to Kekulé benzene

Anthracene and Phenanthrene Anthracene Phenanthrene resonance energy: 347 kJ/mol 381 kJ/mol

An Orbital Hybridization View of Bonding in Benzene

Substituted Derivatives of Benzene and Their Nomenclature

[object Object],General Points

Examples Bromobenzene tert -Butylbenzene Nitrobenzene NO 2 C(CH 3 ) 3 Br

[object Object],[object Object],[object Object],General Points

Ortho, Meta, and Para alternative locants for disubstituted derivatives of benzene 1,2 = ortho (abbreviated o -) 1,3 = meta (abbreviated m -) 1,4 = para (abbreviated p -)

Examples o -ethylnitrobenzene NO 2 CH 2 CH 3 m -dichlorobenzene (1-ethyl-2-nitrobenzene) (1,3-dichlorobenzene) Cl Cl

Table 11.1 (p 407) Certain monosubstituted derivatives of benzene have unique names

Table 11.1 (p 407) Benzaldehyde CH O

Table 11.1 (p 407) Benzoic acid COH O

Table 11.1 (p 407) Styrene CH 2 CH

Table 11.1 (p 407) Anisole OCH 3

Table 11.1 (p 407) Acetophenone CCH 3 O

Table 11.1 (p 407) Aniline NH 2

Easily confused names phenyl phenol benzyl OH CH 2 —

11.9 Physical Properties of Arenes

[object Object],[object Object],[object Object],[object Object],Physical Properties

Reactions of Arenes: Electrophilic Aromatic Substitution H E + E Y + H Y  +  –

12.2 Mechanistic Principles of Electrophilic Aromatic Substitution

מנגנון התמרה אלקטרופילית ב - Alkenes

Step 1: attack of electrophile on  -electron system of aromatic ring ,[object Object],[object Object],H H H H H H E + H H H H H H E +

Step 2: loss of a proton from the carbocation intermediate ,[object Object],[object Object],H H H E H H H + H H H H H H E +

H H H H H + E + H E H H H H + H + H H H H H H H E +

Electrophilic aromatic substitutions include: ,[object Object],[object Object],[object Object],[object Object],[object Object],H E + E Y + H Y  +  –

Table 12.1: Nitration of Benzene + + H 2 O H 2 SO 4 HO NO 2 Nitrobenzene (95%) H NO 2

Nitration of Benzene + + H 2 O H 2 SO 4 HO NO 2 Electrophile is nitronium ion H NO 2 O N O •• + •• • • • •

Where does nitronium ion come from? H 2 SO 4 + O N H O O + •• •• •• • • • • • • •• – O N H O O + •• •• •• • • • • •• – H + O N O •• + •• • • • • H O •• H ••

Step 1: attack of nitronium cation on  -electron system of aromatic ring H H H H H H NO 2 + H H H H H H NO 2 +

Step 2: loss of a proton from the carbocation intermediate H H H NO 2 H H H + H H H H H H NO 2 + מצבים רזונטביים

Table 12.1: Sulfonation of Benzene + + H 2 O heat HO SO 2 OH Benzenesulfonic acid (100%) H SO 2 OH

Sulfonation of Benzene + + H 2 O heat HO SO 2 OH Several electrophiles present: a major one is sulfur trioxide H SO 2 OH O S O O + •• •• •• • • • • • • •• –

Step 1: attack of sulfur trioxide on  -electron system of aromatic ring H H H H H H SO 3 H H H H H H SO 3 – +

Step 2: loss of a proton from the carbocation intermediate H H H SO 3 – H H H + H H H H H H SO 3 – +

Step 3: protonation of benzenesulfonate ion H 2 SO 4 H H H SO 3 – H H H H H SO 3 H H H

Table 12.1: Halogenation of Benzene + + H Br FeBr 3 Br 2 Bromobenzene (65-75%) H Br

Halogenation of Benzene + + H Br FeBr 3 Br 2 Electrophile is a Lewis acid-Lewis base complex between FeBr 3 and Br 2 . H Br

The Br 2 -FeBr 3 Complex ,[object Object],+ Lewis base Lewis acid FeBr 3 Complex • • Br Br • • •• •• •• •• Br Br • • •• •• •• •• FeBr 3 – +

Step 1: attack of Br 2 -FeBr 3 complex on  -electron system of aromatic ring H H H H H H Br Br FeBr 3 – + + FeBr 4 – H H H H H H Br +

Step 2: loss of a proton from the carbocation intermediate H H H Br H H H + H H H H H H Br +

Friedel-Crafts Alkylation of Benzene

Table 12.1: Friedel-Crafts Alkylation of Benzene + + H Cl AlCl 3 tert -Butylbenzene (60%) (CH 3 ) 3 C Cl H C(CH 3 ) 3

[object Object],Role of AlCl 3 (CH 3 ) 3 C Cl •• •• + AlCl 3 • • + (CH 3 ) 3 C Cl •• •• AlCl 3 –

Friedel-Crafts Alkylation of Benzene + + H Cl AlCl 3 Electrophile is tert -butyl cation (CH 3 ) 3 CCl H C(CH 3 ) 3 C CH 3 H 3 C H 3 C +

[object Object],Role of AlCl 3 (CH 3 ) 3 C Cl •• •• + AlCl 3 + (CH 3 ) 3 C + • • + (CH 3 ) 3 C Cl •• •• AlCl 3 – Cl •• •• AlCl 3 – • •

Step 1: attack of tert-butyl cation on  -electron system of aromatic ring H H H H H H H H H H H H C(CH 3 ) 3 + C(CH 3 ) 3 +

Step 2: loss of a proton from the carbocation intermediate H H H C(CH 3 ) 3 H H H + H H H H H H C(CH 3 ) 3 +

Friedel-Crafts Acylation of Benzene

Table 12.1: Friedel-Crafts Acylation of Benzene + + H Cl AlCl 3 1-Phenyl-1-propanone (88%) H O CH 3 CH 2 C Cl CCH 2 CH 3 O

Friedel-Crafts Acylation of Benzene + + H Cl AlCl 3 O CH 3 CH 2 CCl CCH 2 CH 3 O Electrophile is an acyl cation H •• CH 3 CH 2 C O • • + CH 3 CH 2 C O • • +

Step 1: attack of the acyl cation on  -electron system of aromatic ring H H H H H H H H H H H H + O CCH 2 CH 3 + O CCH 2 CH 3

Step 2: loss of a proton from the carbocation intermediate H H H H H H + H H H H H H + O CCH 2 CH 3 O CCH 2 CH 3

Reactions Related to Friedel-Crafts Alkylation ,[object Object],H 2 SO 4 + Cyclohexylbenzene (65-68%) H

Substituent Effects in Electrophilic Aromatic Substitution: הכנסת מתמיר שני לטבעת

הכנסת מתמיר שני לטבעת ,[object Object],[object Object],[object Object]

Table 12.2 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],Generalizations

[object Object],Electron-Releasing Groups OR such as —OH, and —OR are strongly activating

[object Object],Nitration of Phenol HNO 3 + 44% 56% OH OH NO 2 OH NO 2

[object Object],Bromination of Anisole Br 2 90% acetic acid OCH 3 OCH 3 Br

[object Object],Examples ERG = • • • • OH •• OR • • •• • • NH 2 • • NHR • • NR 2

מדוע קבוצות אלה גורמות לאקטיבציה ולהכוונה לעמדות ortho, para הסבר – שתי סיבות מולקולת האם מצבי הביניים לאחר כניסת המתמיר

Substituent Effects in Electrophilic Aromatic Substitution: Strongly Deactivating Substituents

[object Object],Many EWGs Have a Carbonyl Group Attached Directly to the Ring — EWG = — NO 2 — SO 3 H O — CH O — CR O — COH O — COR O — CCl — C N

הסיבות להכוונה לעמדת meta ודאקטיבציה

Nitration of Benzaldehyde HNO 3 75-84% H 2 SO 4 CH O CH O O 2 N

Problem 12.14(a); page 468 Cl 2 62% FeCl 3 Cl CCl O CCl O

Disulfonation of Benzene SO 3 90% H 2 SO 4 SO 3 H HO 3 S

Bromination of Nitrobenzene Br 2 60-75% Fe Br NO 2 NO 2

12.14 Substituent Effects in Electrophilic Aromatic Substitution: Halogens ,[object Object],גורמים לדאקטיבציה חלשה והכוונה לעמדות ortho, para

Nitration of Chlorobenzene ,[object Object],HNO 3 + + 69% 1% 30% H 2 SO 4 Cl Cl NO 2 Cl NO 2 Cl NO 2

[object Object],The Simplest Case AlCl 3 + CH 3 CH 3 CCH 3 99% O CH 3 COCCH 3 O CH 3 CH 3 O

[object Object],Another Straightforward Case CH 3 NO 2 Br 86-90% CH 3 NO 2 Br 2 Fe

Generalization ,[object Object]

[object Object],The Simplest Case Br 2 87% acetic acid strongly activating NHCH 3 Cl NHCH 3 Cl Br

[object Object],Steric effects control regioselectivity when electronic effects are similar 98% HNO 3 H 2 SO 4 CH 3 CH 3 NO 2 CH 3 CH 3

12.16 Regioselective Synthesis of Disubstituted Aromatic Compounds

Factors to Consider ,[object Object]

Synthesis of m-Bromoacetophenone ,[object Object],Br CCH 3 O CCH 3 O Br

Synthesis of m-Bromoacetophenone para meta Br CCH 3 O

Synthesis of m-Bromoacetophenone AlCl 3 Br 2 AlCl 3 CCH 3 O O CH 3 COCCH 3 O CCH 3 O Br

Factors to Consider ,[object Object],[object Object]

Synthesis of p-Nitrobenzoic Acid from Toluene ,[object Object],CH 3 CO 2 H NO 2 CH 3

Synthesis of p-Nitrobenzoic Acid from Toluene nitration gives m -nitrobenzoic acid oxidation gives p -nitrobenzoic acid CH 3 CO 2 H NO 2 CH 3

Synthesis of p-Nitrobenzoic Acid from Toluene HNO 3 H 2 SO 4 Na 2 Cr 2 O 7 , H 2 O H 2 SO 4 , heat CH 3 NO 2 CH 3 NO 2 CO 2 H

File

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (8)

Similar to File

Similar to File (20)

Recently uploaded

Recently uploaded (20)

File

Editor's Notes