Ammonia Reduction of an Alkyne

This mechanism involves addition of an electron, followed by a proton, then addition of a second electron, followed by a second proton. 

Step 1 An electron adds to the alkyne, forming a radical anion. 

Stqj 2 The radical anion is protonated to give a radical 

Step 3. An electron adds to the radical, forming an anion. 

The anti stereochemistry of the sodium-ammonia reduction appears to result from the greater stability of the vinyl radical in the trans configuration, where the alkyl groups are farther apart. An electron is added to the trans radical to give a trans vinyl anion, which is quickly protonated to the trans alkene. 

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FIGURE 9.4 Mechanism of the sodium-ammonia reduction of an alkyne. 

Mechanism of the lithium/ ammonia reduction of an alkyne to produce a trans alkene. 

Mechanism 9-1 Metal-Ammonia Reduction of an Alkyne 407 Mechanism 9-2 Acid-Catalyzed Keto-EnolTautomerism 411 Mechanism 9-3 Base-Catalyzed Keto-EnolTautomerism 413 9-10 Oxidation of Alkynes 414... 

Sodium-Ammonia Reduction of an Alkyne THE OVERALL REACTION ... 

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