Alkenes, Alkynes pt 3
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Transcript of Alkenes, Alkynes pt 3
Alkenes: OxidationOzonolysis
Dihydroxylation with OsO4
Alkenes: OxidationHydroboration oxidation
Alkenes: OxidationCold, alkaline KMnO4
acidic KMnO4
Polymerization of Alkenes• Polymers are large molecules that
contain a large number of repeating units of a small molecule (monomer).
• Biopolymers are typically synthesized by organisms.
• Synthetic Polymers are made in organic laboratories.
Polymerization of AlkenesAlkenes can be used as a monomeric unit
to form chain-growth polymers
styrene
n
polystyrene
Polymerization of Alkenes
Polymerization of AlkenesFor the polymerization, electrophilic addition reactions can be used.
BF3 F3B
In the initiation step an electrophile (BF3) adds to the alkene to form a carbocation intermediate.
Polymerization of Alkenes
F3B+
F3B
Subsequent propagation steps grow the polymer until all monomers are consumed.
Polymerization of AlkenesTermination can also be accomplished by adding a nucleophile.
F3B
n
Nu
F3B
Nu
n
Polymerization of AlkenesAn alternative way to initiate polymerization is starting with a radical initiator.
RO ORD
(hn) 2 ROradicals
RORO
R RR
The radical adds onto the alkene to form a new radical. Propagation is accomplished via subsequent radical additions.
PREPARATION OF ALKENES-ELIMINATION REACTION
Preparation of Alkenes• -Elimination Reactions• Dehydrogenation of alkanes• Dehydration of alcohols• Dehydrohalogenation of alkyl halides
Dehydrogenation of Alkanes
Dehydration of Alcohols
Zaitsev’s Rule
Dehydrohalogenation of RX
CONJUGATED DIENESADDITION & DIELS-ALDER REACTIONS
Reaction of Conjugated Dienes• undergo two-step electrophilic addition
reactios just as do simple alkenes• 1,2 & 1,4-addition
Reaction of Conjugated Dienes
CH2 CH CH CH3 CH2 CH CH CH3
Less Substituted Double Bond(Secondary carbocation)
More Substituted Double Bond(Primary carbocation)
+
Diels-Alder Reaction: Cycloaddition
REACTION OF ALKYNESADDITION, OXYDATION, & ACIDITY OF TERMINAL ALKYNES
Reactivity of Alkynes
Hydrohalogenation
Hydrohalogenation
Halogenation
Hydration
Hydration of Alkyne & Tautomerism
Draw the ENOL tautomers of the following ketones:
Catalytic Reduction
Oxidation
Acidity of Terminal Alkynes
H C C H + NH2 H C C + H3N
Acidity of Terminal Alkynes
-FIN-