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.
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Reactions

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

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Mercuration
Oxymercuration
alkene
alcohol
enol
alkyne
vinyl alcohol
keto
tautomerism
isomerization
20
Resonance stabilized intermediate
enol
keto
21
Note!
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Mercuration
23
Answer Key
24
Mercuration
25
Answer Key
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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

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Hydroboration
alkene
alcohol
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enol
keto
Resonance stabilized intermediate
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Acid
enol is protonated first then loses a proton.
Base
enol loses a proton then regains it.
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Hydroboration
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Answer Key
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Hydroboration Summary

• Alkyne ? Ketone (internal ?) or aldehyde
  (terminal ?).
• Tautomerism enol ? keto.
• Follow non-Markovnikov rule.
• Base catalyzed.

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Hydroboration - Mercuration
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Answer Key
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Reactions

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

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Reduction
alkene
alkane
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Reduction
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Answer Key
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Reactions

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

41
Oxidation
aldehyde
alkene
acid
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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
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Alkylation
48
Alkylation
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Answer Key
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(No Transcript)
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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?