| Metal Acetylide |
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| CATEGORIES ABOUT METAL ACETYLIDE | |
| anions | |
| acetylides | |
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A metal acetylide is an Alkyne that has had a proton (hydrogen) removed from the terminal end by a Metal such as Sodium or an Organolithium . So, for example, the alkyne CH3C≡CH could be Deprotonated to form the acetylide ion CH3C≡C−. Once it has been deprotonated it becomes a strong Nucleophile . Some acetylides, eg. Silver Acetylide or Copper Acetylide , are Explosives . Acetylide ions are very useful in Organic Chemistry reactions in combining carbon chains, particularly Addition and Substitution Reaction s. One type of reaction displayed by acetylides are Addition Reaction s with Ketone s to form Tertiary Alcohol s. In the reaction in ''scheme 1'' the alkyne proton of ''ethyl propiolate'' is deprotonated by N-butyllithium at -78 °C to form lithium ethyl propiolate to which Cyclopentanone is added forming a Lithium Alkoxide . Acetic Acid is added to remove lithium and liberate the free alcohol ''Synthesis of alkyl 4-hydroxy-2-alkynoates'' M. Mark Midland, Alfonso Tramontano, John R. Cable J. Org. Chem. ; 1980; 45(1); 28-29. Abstract . Coupling reactions of alkynes like the Sonogashira Coupling , the Cadiot-Chodkiewicz Coupling , the Glaser Coupling and the Eglinton Coupling often have metal acetylides as intermediates. Several modifications of the reaction with carbonyls are known:
Formation of acetylides poses a risk in handling of gaseous acetylene in presence of metals like eg. Mercury , Silver or Copper , or alloys with their high content ( Brass , Bronze , silver Solder ). REFERENCES |
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