Introduction to Aromatic Chemistry. A First Year Lecture Course by Dr Joachim Steinke (c) 2002.

1.1.Historical Aspects
1.2.Resonance Energy and Reactivity
1.2.1.Valence Bond Representation
1.3.Orbital Picture of Benzene
1.3.1.Frost-Musulin Diagrams
1.4.Aromatic Character
1.5.Hückel Rule
1.6.The Hückel Rule at Work
2.Aromatic Electrophilic Substitution
2.1.General Reaction Profile
2.2. Electrophilic Nitration
2.2.1.Orientation and Reactivity
2.2.2.Ipso Attack
2.5.Friedel-Crafts Alkylation and Acylation
2.5.1. Friedel-Crafts Alkylation
2.5.2.Friedel-Crafts Acylation
2.6.Directing Effects in Disubstituted Benzenes
2.7.Strategies for the Preparation of Disubstituted
2.8.Benzene Diazonium Salts
2.8.1.Primary Aromatic Amines
2.8.2.Reactions of benzene diazonium salts
6.3.1.Strategic use in synthesis
2.9.Formylation Reactions
3.Aromatic Heterocycles
3.1.Five Membered Rings
3.1.1.Reactivity and Orientation
3.2.Six Membered Rings
3.2.1.Reactivity and Orientation
4.Aromatic Nucleophilic Substitution
4.1.The SN2ArMechanism
4.2.Benzyne Mechanism
5.Aromatic Radical Substitution
5.1Radical Substitution Reactions
5.2Related Examples
6.Introduction to 1H-NMR Spectroscopy
6.2.Salient Features of an 1H-NMR Spectrum

To introduce at a fundamental level the area of aromatic chemistry. The course starts
with the introduction of the concept of aromaticity. Mainly benzene and its derivatives
are used to illustrate the most important aromatic substitution reactions. Both
electrophilic and nucleophilic aromatic substitution mechanisms are discussed
including the effect of substituents on reactivity and orientation. Examples are given
to highlight synthetic strategies towards particular substitution patterns. Aromatic
substitution on 5 and 6 membered heterocyclic aromatic compounds as well as
polycarbocyclic compounds are discussed briefly. The course finishes with a “pocket”
guide to NMR spectroscopy and its application in the determination of the structure of
simple aliphatic and aromatic molecules

To be able to define aromaticity. To identify aromatic molecules with the help of
Hückel’s Rule. To apply general reaction profiles towards nucleophilic and
electrophilic aromatic substitution reactions. To describe reactivity and orientation of
both electrophilic and nucleophilic aromatic substitutions with the help of resonance
(canonical) forms for the Wheland and benzyne intermediates. To be able to classify
substituents as either weakly or strongly electron donating or withdrawing and the
consequences with regards to the substitution patterns. To suggest ways in which it
is possible to probe aromatic substitution mechanisms (deuterium isotope effect,
isotope labelling, trapping of intermediates). To be able to identify the actual
nucleophiles or electrophiles of the following reactions and to apply these reactions in
the synthesis of mono-, di- and multiple-substituted aromatic compounds: Nitration,
sulphonation, chlorination, formation of diazonium salts and subsequent reactions
(Sandmeyer reaction, Scholl reaction) Friedel Crafts acylation and alkylation (include
potential side reactions). To have a working knowledge in the use of proton NMR
spectroscopy for the identification of simple aliphatic and aromatic compounds based
on the interpretation of chemical shift, 1st order splitting patterns, magnitude of
coupling constant and “roofing”.

Textbooks and Literature:
All good undergraduate textbooks cover the material presented in this lecture course.
More about NMR spectroscopy can be found in standard spectroscopy textbooks like
Williams and Fleming. An Oxford Chemistry Primer has been dedicated to the
chemistry of aromatic compounds: M. Sainsbury, Aromatic Chemistry, Oxford
University Press, 1991.