Background for Aromatic Compounds
Kekule proposed the structure of benzene in 1865. The carbons in benzene are sp² hybridized, have a bond angle of 120^o, and have a trigonal planar shape.  Benzene can be drawn with all carbons and hydrogens, with just lines, or using a circle in the ring.

Aromaticity, Huckel=s rule
Pi electrons are counted as follows: each double bond counts as two pi electrons, each + charge counts as zero pi electrons, each B charge counts as two pi electrons, each radical counts as one pi electron.  Set the total number of pi electrons as equal to 4n + 2; solve for n.  If the compound is aromatic, then it is cyclic with a continuous ring of overlapping p orbitals and n equals a whole number.  If the compound is antiaromatic, then it is cyclic with a continuous ring of overlapping p orbitals, but n does not equal a whole number.  If the compound is not aromatic, then it is noncyclic or is cyclic without a continuous ring of overlapping p orbitals.

Nomenclature of Aromatic Compounds
C₆H₅CH₃ is named toluene.  C₆H₅OH is named phenol.  C₆H₅NH₂ is named aniline.  C₆H₅OCH₃ is named anisole.  C₆H₅CH=CH₂ is named styrene. A benzene with an aldehyde group is named benzaldehyde.  A benzene with a methyl ketone group is called acetophenone.  A benzene with a carboxylic acid group is named benzoic acid.  The benzene is the parent compound.  Number the ring so that the groups have the lowest possible numbers.  If a special name is used for a benzene derivative, then that group is in position one; then number the other groups. Ortho means that the two groups are on adjacent carbons or on the 1,2 positions.  Meta means that the two groups are separated by one carbon or on the 1,3-positions.  Para means that the two groups are on opposite ends or on the 1,4-positions.  The fused ring structures of anthracene, naphthalene, and phenanthrene are drawn out.

Reactions of Aromatic Compounds
Benzene is halogenated with bromine and iron (III) bromide; chlorine and aluminum chloride; or iodine and nitric acid to give a halobenzene. Nitration of benzene with nitric acid, in the presence of sulfuric acid, produces nitrobenzene. Benzene is sulfonated with sulfur trioxide, in the presence of sulfuric acid, to yield benzenesulfonic acid. In Friedel-Craft alkylation, benzene reacts with aluminum chloride and alkyl halide to form an alkylbenzene.  In Friedel-Craft acylation, benzene reacts with aluminum chloride and an acid halide to form a ketone.

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Kekule proposed the structure of benzene in 1865.  The carbons in benzene are sp² hybridized, have a bond angle of 120^o, and have a trigonal planar shape.  The equation for Huckel=s rule is given.  The criteria for aromatic, antiaromatic, and not aromatic are described.  The special names for the monosubstituted benzenes are listed.  The rules for the nomenclature of aromatic compounds are described.  Ortho, meta, and para definitions are given.  The structures of anthracene, naphthalene, and phenanthrene are drawn out.  The mechanism for electrophilic aromatic substitution is discussed, along with specific examples of other examples.  Halogenation of benzene produces halobenzene.  Nitration of benzene gives nitrobenzene.  Sulfonation of benzene yields benzenesulfonic acid.  The Friedel-Craft alkylation of benzene gives alkylbenzene. The Friedel-Craft acylation of benzene produces a ketone.

This tutorial provides the comprehensive coverage of the chapter with easy introduction and simple illustration. It features:

• Concept map showing interconnections of new concepts in this tutorial and those previously introduced.
• Definition slides introduce terms as they are needed.
• Visual representation of concepts.
• Use of colors to emphasis points.
• Outline of structure.
• Huckel’s rule is explained in detail, with examples.
• Easy-to-follow animations of stated rules of nomenclature.
• Detailed stepwise explanations and animations of reactions and mechanisms.
• Examples worked out step-by-step throughout the tutorial.
• A concise summary is given at the conclusion of the tutorial.

Background Information for Aromatic Compounds

• History Lesson
• Structure of Benzene
• Drawing Benzene
• Determining Aromaticity

Nomenclature of Aromatic Compounds

• Special Names
• IUPAC Nomenclature
• Disubstituted Benzene Derivatives
• Aromatic Fused Rings

Reactions of Aromatic Compounds

• Electrophilic Aromatic Substitution
• Halogenation
• Nitration
• Sulfonation
• Friedel-Craft Alkylation
• Friedel-Craft Acylation