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Alkyne

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Reactions of alkyne that are common to alkene are additions ... Tautomerism enol keto. Follow non-Markovnikov rule. Base catalyzed. 5/16/09. Chapter 8 - Alkyne ... – PowerPoint PPT presentation

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Title: Alkyne


1
Chapter 8
  • Alkyne

2
Properties
  • CnH2n-2
  • Reactions of alkyne that are common to alkene are
    additions and oxidations.
  • Reactions that are specific to alkyne involve
    acidity of ? C ? H (acetylenic) hydrogen.
  • sp hybridization - linear.

3
Alkyne
  • Naming
  • Synthesis
  • Reactions

4
Naming
2,5-Dimethyl-3-hexyne
5
Naming
3,3-Dimethyl-1-butyne
6
Naming
3,3-Dimethyl-4-Octyne
7
Naming
2,5,5-Trimethyl-3-heptyne
8
Naming
2,4-octadien-6-yne
9
Naming
6-Isopropylcyclodecyne
10
Naming
3-Chloro-1-propyne
5-Hexyne-1-ol
3-butyn-2-ol
11
Alkyne
  • Naming
  • Synthesis
  • Reactions

12
Alkyne Synthesis
Dehydrohalogenation of halides
Halogenation of alkene
Halogenation/dehydrohalogenation
13
Alkyne Synthesis
vinylic halides
14
Alkyne
  • Naming
  • Synthesis
  • Reactions

15
Reactions
  • Addition of HX and X2
  • Hydration - mercuration and hydroboration
  • Reduction
  • Oxidation
  • Alkylation

16
Bond Energies
Alkyne reactions are similar to alkenes - center
around the pi bond.
17
Addition of HX and X2
Follow Markovnikovs rule trans addition.
18
Reactions
  • Addition of HX and X2
  • Hydration - mercuration and hydroboration
  • Reduction
  • Oxidation
  • Alkylation

19
Mercuration
Oxymercuration
alkene
alcohol
enol
alkyne
vinyl alcohol
keto
tautomerism
isomerization
20
Resonance stabilized intermediate
enol
keto
21
Note!
22
Mercuration
23
Answer Key
24
Mercuration
25
Answer Key
26
Mercuration Summary
  • Alkyne ? Ketone.
  • Tautomerism enol ? keto.
  • Follow Markovnikov rule.
  • Acid catalyzed.

27
Reactions
  • Addition of HX and X2
  • Hydration - mercuration and hydroboration
  • Reduction
  • Oxidation
  • Alkylation

28
Hydroboration
alkene
alcohol
29
enol
keto
Resonance stabilized intermediate
30
Acid
enol is protonated first then loses a proton.
Base
enol loses a proton then regains it.
31
Hydroboration
32
Answer Key
33
Hydroboration Summary
  • Alkyne ? Ketone (internal ?) or aldehyde
    (terminal ?).
  • Tautomerism enol ? keto.
  • Follow non-Markovnikov rule.
  • Base catalyzed.

34
Hydroboration - Mercuration
35
Answer Key
36
Reactions
  • Addition of HX and X2
  • Hydration - mercuration and hydroboration
  • Reduction
  • Oxidation
  • Alkylation

37
Reduction
alkene
alkane
38
Reduction
39
Answer Key
40
Reactions
  • Addition of HX and X2
  • Hydration - mercuration and hydroboration
  • Reduction
  • Oxidation
  • Alkylation

41
Oxidation
aldehyde
alkene
acid
42
Oxidation
43
Answer Key
44
Oxidation Summary
  • Alkyne ? caboxylic acid and CO2.
  • Shortening the chain.

45
Reactions
  • Addition of HX and X2
  • Hydration - mercuration and hydroboration
  • Reduction
  • Oxidation
  • Alkylation

46
Alkylation
deprotonated
acetylide anion
sodium amide
carbanion
powerful nucleophile
acidic
reaction center
47
Alkylation
48
Alkylation
49
Answer Key
50
(No Transcript)
51
Alkylation Summary
  • Alkyne (shorter) ? Alkyne (longer).
  • Limited to primary alkyl bromides and iodides.

52
Reactions
  • Addition of HX and X2
  • Hydration - mercuration and hydroboration
  • Reduction
  • Oxidation
  • Alkylation

53
Alkyne
  • Sample Problems

54
How would you carry out the following reactions?
55
How would you synthesize the following products
from the given starting material?
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