# Does Wurtz-Fittig-reaction involves Sn1 or Sn2?

Following mechanism is commonly proposed for the Wurtz-Fittig-Reaction:

Picture from Wikipedia

The red marked reaction steps is a nucleophilic substitution (SN). I suppose that this is a SN1 reaction, with an intermediate carbocation, rather than a SN2 reaction. In my opinion the resulting carbocation is good enough stabilized throughout the aromatic ring and therefore SN1 should be preferred, moreover because of the steric hindrance of the aromatic ring.

Is this assumption right? Thanks a lot for your help.

• I’m kind of torn between upvoting this question because you actually thought about it and downvoting because your thoughts are entirely in the wrong direction. Notice that the phenyl cation is not stabilised by resonance and not delocalised over the ring. Quite contrary to your expectations, it is very reactive.
– Jan
Aug 31 '17 at 9:31
• @Jan Ok thanks, the orientation and type of the orbitals I totaly forgot. This article explains this problem further. Therefore it cannot be a Sn1. But a Sn2 neither (massive steric problems). So I assume that there is a total different mechanism. Maybe nevertheless a formation of a Phenyl cation, but through a different mechanism (abstraction the Br as a Bromid through the carban-Anion)? Aug 31 '17 at 11:14
• My best guess is that it’ll be akin to an $\mathrm{S_NAr}$ reaction.
– Jan
Aug 31 '17 at 11:25
• Note that the picture you linked to isn't present on the corresponding English Wikipedia article as of today. Feb 14 '18 at 5:50

• Correct me if this is wrong, but isn't this the mechanism for elimination-addition of benzene, not $\ce{S_NAr}$?