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For the mechanism of wurtz-fittig reaction I got two different ones on the net.

1. From another question on stackexchange: enter image description here

  1. From tutorvista:enter image description here

They are not really the same. In the first one the alkyl group is acting as the nucleophile and as Sn reaction do not occur at sp2 hybridized orbitals, it goes through an SnAr reaction. But in the second one the aryl group is acting as a nucleophile. So the same reasoning does not apply here, because here Sn2 is happening at a primary sp3 hybridized carbon whereas the aryl group is just the nucleophile. So is the second mechanism wrong or I am missing some point?

Neither of the mechanisms really show why we used two different halogens in the alkyl and aryl group (or maybe I can't understand), in fact the first mechanism is using Cl on the alkyl group whereas the second mechanism is using iodine (which is a far better leaving group). But the aryl group has bromine on both. Really confusing if I am to search for explanations myself. Please clear me up.

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  • $\begingroup$ "From another question of stackexchange: " Which SE question did you get it from? I am surprised how SN2 can take place on aromatic ring position. "it goes through an SnAr reaction." I was told that SN2Ar only occurs in presence of electron withdrawing groups like nitro on the ring at ortho/para to the halo group. The given benzene ring has none of it. $\endgroup$
    – Gaurang Tandon
    Feb 14, 2018 at 4:21
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    $\begingroup$ The asker actually asked that very question, that if an Sn2 occurs at that sp2 hybridized carbon. But the answers showed that it was an SnAr. I picked this picture, just to show the case where alkyl group acts as a nucleophile. Maybe I should have picked the picture from the answer. Anyways here's the link: chemistry.stackexchange.com/questions/81983/… $\endgroup$
    – Sami
    Feb 14, 2018 at 5:28

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