[dexangeles]

I'm not really having a hard time digesting this, it's actually pretty straightforward
that's if you follow what's told and not try to understand te reasoning behind it

I believe my book gives a really "useless and lame" explanation for Halogens

it explains that halogens on a benzene (halobenzene) are:

deactivating --- because they are electronegative and induction effect causes it to be slower than benzene

Otho and Para director --- because they have free electrons to donate and stabilize resonance of the carbocation formed thru ortho and para.  The free electron pair donation is insufficient to overcome the electron withdrawing inductive effect of halogen, so it's still slow.

okay, I understand that part, but..

this is the same explanation given for substituents with Oxygen directly connected to the aromatic ring.  But it is stated that oxygen's donation of its electrons is sufficient enough to overcome it's inductive effect; thus, it is activating and an otho para director.

why is oxygen's donation strong enough to overcome the inductive effect, and the halogen's isn't?  you'd think the halogen's donation would be more sufficient because it's trying to overcome a much smaller inductive effect (cause by electronegativity) than what oxygen has to overcome.

any thoughts?

[Demotivator]

same reason as why alkoxides are stronger bases than halides. They are better electron donors due to the alkyl group.

[dexangeles]

this is embarrassing, why didn't i think of the basicity of the substituents :Flush:

thanks  :beerchug:

[movies]

Isn't it also a consequence of better orbital overlap between the p-orbitals on oxygen (2p) and the 2p orbitals of the benzene ring?  The halogens (excepting flourine) all have much larger p-orbitals (3p, 4p, 5p) available for donation and the overlap is much worse.