Alcohols
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What are the reagents in halogenation? [EAS]
• X2 2. FeX3 (catalyst)
How is the electrophile formed in halogenation? [EAS]
• X2 bonds with FeX3 • X-X electrons collapse onto the X bonded to Fe • X+ and FeX4- formed
What is the electrophile in halogenation? [EAS]
X+
What are the reagents in nitration? [EAS]
• HNO3 2. H2SO4
What is the electrophile in nitration? [EAS]
NO2+
How is the electrophile formed in nitration? [EAS]
• Proton transfer from H2SO4 to HNO3 • Conjuate acid of HNO3 (H2NO3) loses water • NO2+ is formed
What are the reagents in sulfonation? [EAS]
• SO3 2. H2SO4
What is the electrophile in sulfonation? [EAS]
SO3
What group is substituted on the ring with sulfonation? [EAS]
SO3H
What are the two types of Friedal-Crafts reactions?
• Alkylation 2. Acylation
What are the reagents in friedel-crafts alkylation? [EAS]
• R-X 2. AlCl3
What is the electrophile in friedel-crafts alkylation? [EAS]
R+
What are the reagents in friedel-crafts acylation? [EAS]
• RCCl=O
Why do halogen atoms on sp2 hybridized carbons not react react to produce electrophiles under conditions of Friedel-Crafts alkylation?
There is a high activation energy to form vinyl and aryl carbocations.
What are three limitations of the Friedel-Crafts alkylation reaction?
• Rearrangements • Fails altogether with benzene having one or more strongly electron-withdrawing groups • Hard to stop reaction at monoalkylation
What are two advantages of Friedel-Crafts acylation over alkylation?
• Rearrangements do not occur 2. Reaction stops at monosubstitution
What reagents are used to reduce an NO2 group to an NH2 group? [EAS modification]
• Sn 2. HCl
What reagents are used to reduce a carbonyl group to a methylene group (e.g. to go from acylation -> alkylation resembling product)
• N2H4 • KOH OR • Zn(Hg) • HCl
What is the general three (3) step mechanism for Electrophilic Aromatic Substitution?
• Generation of electrophile • Attack by electrophile on aromatic ring forming sigma complex • Loss of H+ to reestablish aromaticity
What are the two ways an existing group can influence further substitution? [EAS]
• Orientation 2. Rate
What is an activating group?
A substituent on a benzene ring that increases rate of substitution
What is a deactivating group?
A substituent on a benzene ring that decreases rate of substitution
What is an ortho-para directing group?
A substituent on a benzene ring that directs substituted groups to ortho-para position
What is a meta directing group?
A substituent on a benzene ring that directs substituted groups to meta position