TERMS: Definitions, examples, and
brief explanations
1.
Arenes,
aryl group
2.
Electrophilic
aromatic substitution
3.
Arenium
ion, sigma complex
4.
Activating
groups, deactivating groups
5.
Ortho-/
para- directors, meta- directors
6.
Benzylic
radicals, cations
7.
Conjugated
alkenylbenzenes
KNOW HOW TO:
1. Write resonance structures for intermediate arenium ions formed during a variety of electrophilic aromatic substitution reactions.
2.
Draw
the reaction coordinate for electrophilic aromatic substitution reactions.
3.
Explain
why a Lewis acid catalyst is needed during halogenation and Friedel-Crafts
alkylation/acylation of aromatic compounds.
4.
Know
the identities of the active electrophiles in the various electrophilic
aromatic substitution reactions and the mechanistic steps which produce them
during the reactions.
5.
Carry
out alkylation reactions using appropriate reagent pairs: (a) RX + anhydrous
AlCl3; (b) Alkene + H3O+; (c) ROH + H3O+
6.
Recognize
if a proposed alkylation reaction may be problematic due to
(a)
possibility
of rearrangement of the active electrophile
(b)
presence
of strong electron-withdrawing groups on the ring
(c)
RX
= aryl/vinyl halide
(d)
Possibility
of polyalkylation
7. Use two-step procedure to prepare alkylbenzenes where alkyl group is unbranched (Acylation followed by Clemmensen reduction)
8.
Recognize
whether a substituent is likely to activate or deactivate the ring toward
further substitution.
9.
Recognize
whether a substituent is an ortho-/para- director or a meta- director.
10.
Explain
why moderately and strongly deactivating groups are all meta- directors (using
resonance contributors of the intermediate arenium ions).
11.
Explain
why activating groups are all ortho-/para- directors (using resonance
contributors of the intermediate arenium ions).
12.
Explain
why halogens are ortho-/para- directors, even though they are weakly
deactivating.
13.
Halogenate
side chains to prepare benzylic halides.
14.
Write
resonance structures (contributors) for benzylic radicals and cations: use
these to account for their stability.
15.
Predict
products of addition reactions of various alkenyl benzenes.
16.
Predict
products of elimination reactions of benzylic halides and/or alcohols.
17.
Predict
the SN products of various reactions undergone by benzylic halides
(also refer to Chapt.6).
18.
Predict
products resulting from the oxidation of side-chains (e.g., alkyl, alkenyl,
alkynyl, acyl)
19.
Recognize
the different products that can be obtained by changing the order of reactions
in multi-step syntheses ( due to differences in the directing ability of
different substituents).
20.
Predict
relative product ratios (i.e.,
major/minor products) in substitution reactions of various disubstituted
benzenes.
21.
Use
ozonolysis products to determine the structure of Birch reduction products.
REACTION
MECHANISMS:
1.
Nitration
2.
Halogenation
3.
Sulfonation
4.
Friedel-Crafts
alkylation, acylation
5.
Addition
reactions of various alkenyl benzenes via C+/C. intermediates.
6.
SN1/SN2
reactions of benzyl halides
7.
Elimination
reactions of benzyl halides/alcohols.
8.
Birch
reduction
CONVERSION
REACTIONS:
1.
Aromatic
compound à acylated compound à alkylbenzene (unbranched side-chain)
2.
Aromatic
compound à acylated compound à various electrophilic aromatic
substitution reactions
3.
Aromatic
compound à acylated compound à 2o alcohol à various reactions of alcohols
4. Aromatic compound à acylated compound à oxidation product
5.
Aromatic
compound à acylated compound à 3o alcohol (containing more carbon atoms) à various reactions of 3o alcohols
6.
Aromatic
compound à alkylated compound à various electrophilic aromatic
substitution reactions
7.
Aromatic
compound à alkylated compound à benzylic halide à various SN and E
reactions of benzylic halides
8. Aromatic
compound à
alkylated compound à oxidation product
9. Aromatic
compound à
acylated compound à gem-dichloro compound à alkynyl benzene