Organic Chemistry
Chapter 4
Part II
All About Reactions with
Aromatic Compounds
Nanoplasmonic Research Group
How to Name It ??
• Many Common Names
• Benzene, Toluene, Cumene, etc (p. 123)
• Monosubstituted Benzenes Systematic Nam
es as Hydrocarbons with “~benzene”
• When a benzene ring is a substituent, the t
erm phenyl is used (for C6H5-)
• You may also see “Ph” or “ϕ” in place of “C
6H5-”
• “Benzyl” refers to “C6H5CH2-”
Disubstituted Benzenes
• Relative positions on a benzene ring
– ortho- (o) on adjacent carbons (1,2)
– meta- (m) separated by one carbon (1,3)
– para- (p) separated by two carbons (1,4)
• Describes reaction patterns
Recall from the previous PPT slides
Electrophiles in EAS
Energy
The Mechanism of EAS
Reaction Coordinate
Alkylation and Acylation
• Aromatic substitution of alkyl or
acyl group for H
• Aluminum chloride promotes the for
mation of the carbocation
Substituent Effects in Aromatic Rings
• Substituents can cause a compound to be
(much) more or (much) less reactive than
benzene
• Substituents affect the orientation of the rxn
– the positional relationship is controlled
– ortho- and para-directing activators, ortho- and
para-directing deactivators, and meta-directing
deactivators
Summary of Directing Effects
How to distinguish them ?
• Ortho, para-directing groups
– Substituents can stabilize carbocation
intermediate
– Electron-donating group & Electronwithdrawing group on condition that the
atom attached to the aromatic ring has an
unshared electron pair
• Meta-directing groups
– In general, the atom directly attached to the
benzene ring will carry a positive charge
Steric Effect in EAS
• Please make sure to draw resonance
contributors in the middle of EAS as
many as possible by yourself !!!