Partial hydrogenation
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.
- Reagents
- H2; Lindlar catalyst
- Conditions
- Catalytic partial reduction
- Reaction class
- Partial hydrogenation
- Equation
- CH3C≡CCH3 + H2 -> cis-CH3CH=CHCH3
Overview
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.
Transformation
- Equation
- CH3C≡CCH3 + H2 -> cis-CH3CH=CHCH3
- Reactants
- But-2-yne + Hydrogen
- Products
- cis-But-2-ene
- Reagents
- H2; Lindlar catalyst
- Environment
- Catalytic partial reduction
- Reaction class
- Partial hydrogenation
- Mechanism
- surface-catalysed syn hydrogenation
- Evidence level
- textbook extension
Scope and limitations
- Scope
- Symmetrical internal alkyne; syn addition gives the cis (Z) alkene.
- Limitations
- Ordinary active Pd/C promotes further reduction; catalyst choice determines the endpoint.
Related reactions
- Dissolving metal reduction: But-2-yne → trans-But-2-ene
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.
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.