Question

Orgo II Tutorial: Ortho/Meta/Para Directors

Answer 1

\({\bf{Overview:}}\) as a reminder, we use ortho/meta/and para designators to label the position of a functional group with reference to an existing functional group

Answer 2

if we use group X as the reference position, then O is in the ortho position, P is in the para position, and M is in the meta position

remember you can also label these w/ carbon #'s. O is in the 1,2 positions, M is in the 1,3 positions, P is in the 1,4 positions. because of steric effects, P is often preferred over the ortho position

Answer 3

to determine whether the incoming group will be an ortho/para OR a meta director, we can examine the behavior of the existing group

electron donating groups tend to be O/P directors while electron withdrawing groups tend to be M directors. this reasoning comes from the relative # of stable resonance structures from o/p attacks vs. m attacks.

Answer 4

(this is kind of a pain to draw out w/ the drawing tool so I will probably draw them by hand and upload them)

Answer 5

now to demonstrate meta directors, we will use NO2 which is a very very strong meta director (don't confuse this with NH2)

Answer 6

\({\bf{Activating~vs.~Deactivating:}}\)

electron donating groups are called "activating" because their donations make the benzene ring more nucleophilic and primed for electrophiles to attack (OP directors)

electron withdrawing groups are called "deactivating" because their withdrawals make the benzene more electrophilic and less readily attacked by electrophiles (M directors)

the major exception being halogens which are electron-withdrawing O/P directors that are de-activating

Answer 7

regarding situations with mixes of OP directors and M directors: activating groups take priority over de-activating groups

Answer 8

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is Organic Chemistry 12th edition by Solomons, et. al.