Alkynes

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Alkynes

• Reaction
• Acidity
• Synthesis

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s-Complex of Acetylene
p-Bonds
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Hydrocarbon Comparison
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Alkyne Nomenclature
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Enes with Ynes
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Endiyne Antitumor Agents
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Catalytic Hydrogenation
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Lindlars Catalyst
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H2 on a Poisoned Catalyst Prevents
Over-Reduction cis Alkenes
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Dissolved Lithium in NH3trans Alkenes
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Addition of HX
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Br2 Addition
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Oxymercuration HydrationMarkovnikov
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Enol Keto TautomerizationIntermolecular
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Oxymercuration Mechanism
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Hydroboration HydrationAnti-Markovnikov
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Hydroboration Mechanism
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Draw the Products
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Ozonolysis
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Acidity of Terminal Alkynes
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Acetylide Formation
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Alkylation of Acetylide IonsHomologations using
SN2 rxn
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Multi-step Syntheses
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Retrosynthetic AnalysisBegin with the Product
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Fill in the Reagents
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How Many Steps?
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5 Steps
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Nucleophilic Addition
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Acetylide Addition to Ketones and Aldehydes
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Nucleophilic addition to Benzaldehyde
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Synthesis Problem
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Six separate steps(each individual reaction is
denoted with a number)
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An unknown compound (A) has a formula of C11H14.
Treatment of A with H2/Pd-carbon gives B
(C11H20). Treatment of A with H2 on a Lindlar
catalyst gives C (C11H16). Ozonolysis of C
followed by workup with Zn, HOAc affords
formaldehyde and the tricarbonyl compound shown
below.
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Schematic of the Problem
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• An initial approach to this problem is to
  determine the number of degrees of unsaturation
  in each of the molecules A, B, and C.
• When A (C11H14, 5o unsat.) is hydrogrenated, B
  (C11H20, 2o unsat.) is formed. That means that 3
  p bonds reacted (3 mol. equivalents) to form B.
• When A is treated with H2 over a Lindlar
  (poisoned) catalyst, 1 mol equiv. of H2 reacts.
  Since this reaction is specific for the reduction
  of alkynes to alkenes, 2 of the 3 p bonds in A
  are in the form of a triple bond. The remaining
  p bond must be an alkene.
• We have accounted for three of the five degrees
  of unsaturation in A, therefore the other two
  must be rings since they do not react with H2.

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Propose Structures for A, B, and C