Ch. 18

In the presence of iron, an ___________________reaction is observed between benzene and bromine.

electrophilic aromatic substitution

Iron tribromide is a is a __________________that interacts with Br2 and generated Br+ which is sufficiently electrophilic to be attacked by benzene.

Lewis acid

Electrophilic aromatic substitution involves two steps.

1- formation of the sigma complex 2- deprotonation to restore aromaticity

Sulfur trioxide is a very powerful

electrophile

Sulfur trioxide is present

in fuming sulfuric acid.

Benzene reacts with SO3 in a reversible process called

sulfonation

A mixtrue of sulfuric acid and nitric acid produces the

nirtonium ion (NO2+)

Benzene reacts with the nitronium ion in a process called

nitration

A nitro group can be reduced to an

amino group

Friedel-Crafts alkylation enables the installation of an alkyl group on

an aromatic ring

When choosing an alkyl halide, the carbon aton connect to the halogen in a Friedel-Crafts alkylation must be

SP3 hybridized.

When treated with a Lewis acid, an acyl chloride will generate an

acylium ion, which is resonacne stabilized and not susceptible to carbocation rearrangements.

When a Friedel-Crafts acylation os followed by a Clemmensen reduction the net result is the installation of an

alkyl group.

An aromatic ring is activated by a methyl group with is an

ortho-para director

all activators are

ortho-para directos

A nitro group

deactivates an aromatic ring and is a Meta director

Most deactivators are

meta directors

Strong activators are characterized by the presence of a

lone pair immediately adjacent to the aromatic ring.

Strong deactivators are powerfully electron-withdrawing

either by resonance or induction

When multiple substituents are present the more powerful

activating groups dominates the directing effects

In a nucleophilic aromatic substution reaction the aromatic ring is attacked

by a nucleophile.

A nucleophilic aromatic substitution has three requirements

1- the ring must contain a powerful electron-withdrawing group (usually a nitro group).2- the ring must contain a leaving group. 3- the leaving group must be either ortho or para to the electron-withdrawing group.

An elimination-addition reaction occurs via a

benzyne intermediate.

Which of these is the rate-determining step in the electrophilic aromatic substitution of benzene?

Formation of the sigma complex

What group os incompatable with Friedel-Crafts reaction?

Nitro groups