ORGANIC CHEMISTRY II
EXAM I MATERIAL REVIEW
Spring Semester Week 4, 2013
I.
Chapter 15: Radicals
 Free Radical Halogenation of Alkanes:
Initiation-Propagation-Termination steps
 General Features of Free Radicals (more and less stable radicals)
 Selectivity in free radical halogenation
 Bromination (more selective) versus Chlorination (less selective)
 Hydrohalogenation of alkenes in the presence of peroxides (free radical
mechanism) –“anti-markovnikov addition”
 Allylic Halogenation
 Reagents used (halogen free radicals; NBS)
 Product mixtures in allylic halogenation (whenever two different resonance
structures can be drawn for an allylic radical)
II.
Chapter 16: Conjugation, Resonance, and Dienes
 Conjugation: minimum structures
 1,3-dienes; allylic carbocations (remember allylic radicals too)
 Review of Resonance structures
 Classification of Dienes
 Electrophilic additions reactions of conjugated dienes (hydrohalogenation)
 1,2- versus 1,4-addition
 Kinetic versus Thermodynamic factors
 Diels-Alder Reactions:
 Dienophile reactivity
 Stereospecificity
 Formation of bicyclic products (endo products are more favorable)
 Alkyne dienophiles
III.
Chapter 17: Benzene and Aromatic Compound
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Structural features of aromatic compounds
Why is benzene not 1,3,5-cyclohexatriene?
Criteria for aromaticity… Hückel’s Rule (4n + 2)
Examples of aromatic compounds
 Annulenes
 Fused aromatic rings
 Aromatic Heterocycles: pyridine versus pyrrole
 Aromatic ions: Reactions which involve aromatic transition states (including
those which are ionic –comparison of cyclopentadiene and cycloheptatriene
derivatives)
IV:
Chapter 18: Electrophilic Aromatic Substitution (EAS)
 General mechanism (two step: addition followed by elimination)
 Reaction Profile (rate determining step is the formation of the carbocationic
-intermediate)
 Common EAS Reactions: Nitration; Sulfonation; Halogenation; Friedel-Craft’s
Alkylation; Friedel-Craft’s Acylation; Reactions with Carbocations
 Rearrangements in Friedel-Craft’s Alkylations
 EAS Reactions of mono-substituted benzenes (to give disubstituted benzenes)
 Effects of substituents towards rate of reaction: Activating versus Deactivating
substituents
 Effects of substituents in the selectivity of the reaction (orientation of substitution:
ortho-para or meta directing substituents)
 Determining the electronic effects of substituents: electron releasing versus electron
withdrawing substituents
 Inductive (through -bonds) and resonance (through -bonds) effects
 Synthesis of disubstituted benzenes from benzene (which substituent to add first)
 Side Chain Reactions:
 Benzylic bromination (with NBS)
 Functionalizing the benzylic bromide further (to prepare alkenes, vic-dihalides,
epoxides, alkynes, etc)
 Oxidation of alkyl benzenes (into benzoic acid)
 Reduction of aryl ketones to alkyl benzenes (Clemensen Reduction): a possible route
to make alkyl benzenes after acylation (thus avoiding carbocation rearrangements)
 Multistep Syntheses
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