Alkyne Reaction Video

Alkyne reaction  - video are now available. 12/18/2008

• Acetylide ion reaction ( IMPORTANT) - this is how to enlarge the carbon chain
• Elimination (from Alkane to make Alkyne)
• Addition
• Hydrobonation ( making Ketone instead of alochol)
• Cleavage

Summarize Alkyne reaction video ( more details are below the video)

Acetylide ion - a great ion to start a synthesis! Much often use in alkylation (a reaction to increase Carbons in the final product)  Treating Alkyne with a Strong Base, one hydrogen will be plug off and form acetylide ion.

1,2,3 represents the carbons. The leaving group bromide will go away and the carbon 3 will bonds to the acetylide ion in the end.

Special Topic: Terminal Alkyne v.s Internal Alkyne

Internal Alkyne forms cis and trans alkene 

• Cis Alkene - Metal catalyst and hydrogens are reacts on the surface of the catalyst, hence syn addition of hydrogen occurs.
• Trans Alkene - Ammonia at the liquid state require a dry ice to keep the ammonia "cool".  Sodium and Lithium has a strong tendency to lose the electron and this triggers the reaction. The end product of alkyne reaction has both cis and trans alkenes at the equilibrium state. Because Trans is more stable, therefore, the product favors trans alkene.

  Note: Easy to remember that trans alkene is always favorable than the cis alkene; yet, in order to obtain a cis Alkene, the Mental catalyst should be used

  	Lindlar/ Catalyst	Na or Li/Ammonia at (-78oC)
  	Cis Alkene	Trans Alkene

  How to make following products from Alkyne?

 Ketone can be made from internal alkyne by adding water in acid catalyst!