Trans Alkenes These can be produced by the action of sodium metal in liquid ammonia. Na,NH3 HaC H H3C-C≡C-C2H5 H `C2H5 An electron is added to the triple bond,generating a radical anion,which is protonated to generate a vinyl radical. HR、 H R一CO N C=C +:N H H R H alkyne vinyl radical The radical accepts another electron which produces an anion,which in turn gets protonated,giving the alkene with anti stereochemistry H H H R most stable trans trans alkene The anti stereochemistry arises from the two alkyl groups being as far away from each other as possible at the vinyl radical stage. Ch09 Alkynes (landscape) Page 11Ch09 Alkynes (landscape) Page 11 Trans Alkenes These can be produced by the action of sodium metal in liquid ammonia. An electron is added to the triple bond, generating a radical anion, which is protonated to generate a vinyl radical. The radical accepts another electron which produces an anion, which in turn gets protonated, giving the alkene with anti stereochemistry. The anti stereochemistry arises from the two alkyl groups being as far away from each other as possible at the vinyl radical stage. H3C C C C2H5 H3C H H C2H5 Na, NH3