Chapter 6: Addition Reactions of Alkenes
Hydrogenation of Alkenes
Reaction Type: Electrophilic Addition
Summary
Alkenes can be reduced to alkanes with H
2
in the presence of metal catalysts such as Pt, Pd, Ni or Rh.
The two new C-H
s
bonds are formed simultaneously from H atoms absorbed into the metal surface.
The reaction is
stereospecific
giving only the
syn
addition product.
This reaction forms the basis of experimental "
heats of hydrogenation
" which can be used to establish the stability of isomeric alkenes.
Related reactions
Hydrogenation of alkynes
CATALYTIC HYDROGENATION
Step 1:
Hydrogen gets absorbed onto the metal surface.
Step 2:
Alkene approaches the H atoms absorbed on the metal surface.
Step 3:
C=C
reacts with the H atoms on the surface forming the two new C-H
s
bonds.
