Distinguishing Test of Terminal and Non Terminal Alkynes
The trans-alk...
Question
The trans-alkenes are formed by the reduction of alkynes with
A
H2−Pd/C,BaSO4
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B
Sn−HCl
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C
Na/liq.NH3
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D
NaBH4
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Solution
The correct option is CNa/liq.NH3 Sodium metal in liquid ammonia reduces alkynes with anti stereochemistry to give trans alkenes. The reduction is selectively anti since the vinyl radical formed during reduction is more stable in trans configuration.Sodium atom donates an electron to alkyne which after H−abstraction from NH3 forms vinylic radical. Transfer of another electron gives a vinylic anion, which is more stable in trans form. This in turn gives trans-alkene after H−abstraction from NH3