April 17, 2024, 09:07:49 PM
Forum Rules: Read This Before Posting

Topic: Halogenation  (Read 12201 times)

0 Members and 1 Guest are viewing this topic.

Offline Schrödinger

  • Chemist
  • Sr. Member
  • *
  • Posts: 1162
  • Mole Snacks: +138/-98
  • Gender: Male
Re: Halogenation
« Reply #15 on: April 23, 2010, 01:21:54 AM »
If Br was missing just ONE electron it would be called a Free Radical; and would end up attacking the H on the methyl instead.

Since Br is 2 electrons short, it makes sense that it attacks the double bond on the aromatic ring, and then the rest of the rxn follows as showed in that flash.
A free radical is just a neutral atom. There are no electrons missing.
FeBr3 is a Lewis acid (accepts a pair of electrons). So, it causes Br2 to split into Br+ and Br-. Br- is accepted by FeBr3, since Br- is a Lewis base.

Why does it refer to Br as Br+ instead of Br 2+ in that case?
So, after Br2 splits, what's left is Br+, because Br- is accepted by FeBr3. This is what attacks the electron rich benzene ring.
"Destiny is not a matter of chance; but a matter of choice. It is not a thing to be waited for; it is a thing to be achieved."
- William Jennings Bryan

Sponsored Links