Advices For Studying Organic Chemistry

hydrogen and bind the hydrogen to the surface.

2) The collision of an alkene with the surface bearing adsorbed hydrogen causes

adsorption of the alkene.

3) A stepwise transfer of hydrogen atoms take place, and this produces an alkane

before the organic molecule leaves the catalyst surface.

4) Both hydrogen atoms usually add form the same side of the molecule (syn

addition).

Figure 7.9 The mechanism for the hydrogenation of an alkene as catalyzed by
finely divided platinum metal: (a) hydrogen adsorption; (b) adsorption
of the alkene; (c) and (d), stepwise transfer of both hydrogen atoms to
the same face of the alkene (syn addition).

Catalytic hydrogenation is a syn addition.

CC Pt CC

HH

HH

+

7.14A SYN AND ANTI ADDITIONS

1. Syn addition: