Master Organic Chemistry Reaction Guide

Partial reduction of alkynes to trans alkenes using sodium and ammonia

Description: Alkynes treated with sodium in ammonia are reduced to trans alkenes. Alternatively, potassium in ammonia can also be used.

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5 thoughts on “Partial reduction of alkynes to trans alkenes using sodium and ammonia

  1. Why is the radical anion able to undergo flipping when there is a pi bond? Does that require a great amount of energy to first break the pi bond, flip and then reform the pi bond again?

    1. I was wondering the same thing….? Prehaps the alkyne pi bond cleavage actually takes electrons from each of the separate pi bonds which allows temporary alkane rotation to form the more stable trans intermediate?

      1. As I understand it, the pi bond doesn’t “block” rotation like a rigid beam, but renders rotation unfavorable because there would be no stabilizing overlap in the intermediate: “if it’s not broken, don’t fix it”. If the radical system destabilizes the cis isomer enough, maybe breaking the remaining pi bond would be less unstable by comparison, and no longer inhibitive?

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