|Chapter 9 : Alkynes|
MECHANISM FOR THE REDUCTION OF ALKYNES WITH Na / NH3
Sodium transfers an electron to the alkyne giving a radical anion - electron replusion of the single electron and the lone pair forces them to be trans to each other and this defines the stereochemistry of the product.
The radical anion removes a proton from the ammonia in an acid / base reaction.
A second atom of sodium transfers another electron to the alkyne giving a vinyl carbanion. The stereochemistry is generated at this step - the alkyl groups are trans.
The carbanion removes a proton from the ammonia in an acid / base reaction to give the trans-alkene.
|© Dr. Ian Hunt, Department of Chemistry|