Some surface catalyzed reactions involve more than one type of surface site. An example of

this type of catalytic reaction is the isomerization of $n-$pentane to isopentane which occurs on

a $P\frac{t}{A}{l}_2{O}_3$ catalyst.

$C{H}_{2}C{H}_{2}C{H}_{2}C{H}_{2}C{H}_3(C{H}_3{)}_{2}CHC{H}_{2}C{H}_3$

The mechanism for this reaction is as follows:

$N=n-$pentane, $N^{?}==n-$pentene,

$I=$ isopentane, and $I^{?}==$isopentene

$(1)Nharr{N}^{?}=+H_2$

Pt$-$catalyzed

$(2)N^{?}=+**harr{N}^{?}=**$

on $A{l}_2{O}_3$

$(3)N^{?}=**I^{?}=**,$ on $A{l}_2{O}_3$

$(4)I^{+**}harr{I}^{+}+**,$ on $A{l}_2{O}_3$