Dissolving metal reduction
Successive electron transfers and protonations convert the triple bond into a double bond. The intermediate sequence favours the less crowded arrangement that gives trans-but-2-ene, so this is not the same process as hydrogen delivery on a metal surface.
- Reagents
- Na or Li; liquid NH3
- Conditions
- Dissolving-metal conditions
- Reaction class
- Dissolving-metal reduction
- Equation
- CH3C≡CCH3 + 2[H] -> trans-CH3CH=CHCH3
Overview
Successive electron transfers and protonations convert the triple bond into a double bond. The intermediate sequence favours the less crowded arrangement that gives trans-but-2-ene, so this is not the same process as hydrogen delivery on a metal surface.
Transformation
- Equation
- CH3C≡CCH3 + 2[H] -> trans-CH3CH=CHCH3
- Reagents
- Na or Li; liquid NH3
- Environment
- Dissolving-metal conditions
- Reaction class
- Dissolving-metal reduction
- Mechanism
- electron-transfer reduction and protonation
- Evidence level
- textbook extension
Scope and limitations
- Scope
- Internal alkyne giving the trans (E) alkene.
- Limitations
- [H] denotes reducing equivalents; this equation is not hydrogen-gas catalysis.
Related reactions
- Partial hydrogenation: But-2-yne → cis-But-2-ene
The alkyne binds to the catalyst surface and receives both hydrogen atoms from the same face. This syn addition gives cis-but-2-ene; the deactivated Lindlar catalyst helps limit further reduction to butane.
References
- Organic Chemistry: Reduction of AlkynesJohn McMurry · OpenStax Organic Chemistry · 2023
Supports functional-group chemistry used to curate the linked examples. Checked 2026-09-16; named examples are applications of textbook scope, without claimed experimental yields.