radicalii alchil in mare parte sunt S(I) orienteaza intrarea unui nou subst. in o- si p-
in acest caz putem avea:
1-R-2-X-4-Y
1-R-2-Y-4-X
1-X-2-R-4-Y
1-X-2-Y-4-R
1-Y-2-R-4-X
1-Y-2-X-4-R
=> 6 izomeri