All About Reactions with Aromatic Compounds Nanoplasmonic Research Group Organic Chemistry Chapter 4 Part II

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 te rm phenyl is used (for C 6 H 5 -) You may also see “Ph” or “ ϕ ” in place of “C 6 H 5 -” “Benzyl” refers to “C 6 H 5 CH 2 -”

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

The Mechanism of EAS Reaction Coordinate Energy

Alkylation and Acylation Aromatic substitution of alkyl or a cyl 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 pa ra-directing deactivators, and meta-directing dea ctivators

Summary of Directing Effects

How to distinguish them ? Ortho, para-directing groups –Substituents can stabilize carbocation intermediate –Electron-donating group & Electron- withdrawing 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 !!!