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Chapter 5

The document summarizes key topics in organic chemistry including the nomenclature, preparation, and reactions of alkenes. It discusses how alkenes are named based on parent hydrocarbon chains and geometric isomers. Common preparation methods include dehydration of alcohols, elimination reactions, and hydrogenation of alkynes. Reactions covered include additions of hydrogen halides, halogens, water, borane, and hydrogen. The document also examines epoxidation, ozonolysis, and polymerization of alkenes.

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Mina1212
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51 views45 pages

Chapter 5

The document summarizes key topics in organic chemistry including the nomenclature, preparation, and reactions of alkenes. It discusses how alkenes are named based on parent hydrocarbon chains and geometric isomers. Common preparation methods include dehydration of alcohols, elimination reactions, and hydrogenation of alkynes. Reactions covered include additions of hydrogen halides, halogens, water, borane, and hydrogen. The document also examines epoxidation, ozonolysis, and polymerization of alkenes.

Uploaded by

Mina1212
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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ORGANIC CHEMISTRY

Dr Nam T. S. Phan
Faculty of Chemical Engineering
HCMC University of Technology
Office: room 211, B2 Building
Phone: 38647256 ext. 5681
Email: ptsnam@hcmut.edu.vn
1
Chapter 5: ALKENES
An sp2
hybridized
carbon

2
NOMENCLATURE OF ALKENES
The IUPAC name of an alkene is obtained by replacing
the “ane” ending of the corresponding alkane with “ene”

• Ethylene is an acceptable synonym for ethene in the IUPAC


system
• Propylene, isobutylene and other common names ending in
“ylene” are NOT acceptable IUPAC names
3
Determine the parent
hydrocarbon – the
longest continuous
carbon chain containing
the C=C

4
Note: Alkenes can have geometric isomers

5
PREPARATION OF ALKENES
Dehydrations of alcohols
Acid

isomerization
6
isomerization 7
Eliminations of alkyl halides

Base

8
Alkyne hydrogenations
Pd/CaCO3 + Pb(OAc)2 / quinoline

9
Witttig reaction

10
Using less
sterically
hindered alkyl
halide

11
Stereoselectivity of Witttig reaction Æ depends
on the ylide structure

12
REACTIONS OF ALKENES
Additions of hydrogen halides (AE)

More stable

Markovnikov’s rule 13
Carbocation rearrangement

More stable

14
15
More stable
Stereochemistry

Racemic mixture 16
Already has 1 asymmetric carbon

17
2 asymmetric carbons are created

18
Additions of hydrogen bromide (AR)

Electrophilic addition (AE)

Radical addition (AR) – only for HBr 19


Reaction
mechanism:

20
Additions of halogens

21
Major
addition
product –
NOT a
dihalide

22
Stereochemistry

23
24
Stereochemistry
2 asymmetric carbons are created

Trans-2-butene Æ meso compound 25


Additions of water – hydration reactions
Water is too weakly acidic to allow the hydrogen to act
as an electrophile

Markovnikov’s rule

H2SO4, H3PO4…
26
Reaction
mechanism:

Carbocation
rearrangement
might occur

27
Alcohols by oxymercuration-reduction

Markovnikov’s rule

No carbocation formation, no rearrangement

28
Additions of borane: hydroboration-oxidation

29
Regioselectivity:

Anti-Markovnikov

30
Additions of hydrogen – hydrogenation

31
Reaction mechanism:

Syn addition

32
Stereochemistry

33
34
Alkene epoxidations – Anti hydroxylations

35
Stereochemistry

36
Reactions of epoxides

37
38
Stereochemistry Anti additions

39
Syn hydroxylations of alkenes

40
Reaction mechanism: Syn additions

41
Permanganate cleavage of alkenes

42
Ozonolysis of alkenes

43
In the presence of an oxidizing agent, the products
will be ketones / carboxylic acids
44
Polymerizations

45

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