Chapter 16 The Chemistry of Benzene Derivatives

2 MorphineValium

Aromatic Hydrocarbons Common sources: coal and petroleum Physical properties: – Tend to be insoluble in water – MP’s relatively high – BP’s similar to molecules of similar structure and symmetry Each additional C atom adds 20-30°C to the BP

Common Nomenclature 4

IUPAC Nomenclature Monosubstituted benzenes are named as other hydrocarbons, with –benzene as the parent name Alkyl-substituted benzenes (arenes) are named in two ways: 1)If the alkyl group has 6 or fewer carbons, it is named as the substituent and the benzene ring is the parent 5

2)If the alkyl chain has more than 6 carbons, then the benzene ring is the substituent and is called a “phenyl” group A phenyl group can be represented a few different ways Don’t confuse a phenyl group with a benzyl group 6

Disubstitued benzenes can be named in two ways: – Using o, m, or p – Using numbers 7

Nomenclature Principle groups – If a substituent has highest priority, it is assumed to be on carbon #1 – If none of the substituents has priority over the others, cite them in alphabetical order 8

Numbering is required when more than two substituents are present Recall priorities: carboxylic acid > anhydride > ester > acid halide > amide > nitrile > aldehyde > ketone > alcohol (phenol) > thiol > amine Nomenclature of Benzene Derivatives

Problems Name the following compounds: 10

Electrophilic Aromatic Substitution 11

Halogenation of Benzene Compare with the addition product for that of an alkene Electrophilic Aromatic Substitution Reactions of Benzene

Mechanism of Halogenation Electrophilic Aromatic Substitution Reactions of Benzene

Mechanism of Halogenation Electrophilic Aromatic Substitution Reactions of Benzene

15 Recall:

Three Mechanistic Steps in EAS 1. Generation of an electrophile 2. Nucleophilic reaction of the  electrons of the aromatic ring with the electrophile 3. Loss of a proton from the carbocation to form a substituted aromatic compound 16

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Problem 1)Monobromination of toluene gives 3 products. Draw the entire mechanism for the formation of one product and draw the other two. 2)Draw the product(s): 18

Nitration of Benzene Mechanism: Electrophilic Aromatic Substitution Reactions of Benzene

Nitration of Benzene Electrophilic Aromatic Substitution Reactions of Benzene

Reduction of Nitro-substituted Benzene Rings to Arylamines Also works with SnCl 2 21

Sulfonation of Benzene Mechanism: 22

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Problems 1)Draw the reactants required to produce the molecule below: 2)Draw the products for each step: 24

Friedel-Crafts Alkylation of Benzene Compare the role of AlCl 3 with that of FeBr 3 in the bromination reaction 25

Limitations to Friedel-Crafts Alkylation 1)R must be an alkyl halide 2)The benzene ring cannot have amino or strongly electron withdrawing substituents 26

3)Reaction often does not stop after the first substitution 4)Rearrangement products are often produced 27

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Hydride Shift: Alkyl Shift: 29

Problems Give the products for the following reactions: 30