I was told by my teacher that the following reaction proceeds through SNi:

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Moist $\ce{Ag2O}$ is basically $\ce{AgOH}$, what role does it play in this reaction's mechanism? I think this is what happens, but I am not sure:

  1. $\ce{AgOH}$ attacks $\ce{Cl-}$ and during this process the $\ce{Ag-O}$ bond breaks and an intimate ion pair is formed between the carbocation and $\ce{Cl-}$.
  2. Since a partial bond still exists between $\ce{Ag}$ and $\ce{O}$, $\ce{O}$ is forced to attack from the same side from where $\ce{Cl-}$ left and the reaction proceeds to completion without Walden inversion.

Is my reasoning correct? Or is there a different mechanism?

  • $\begingroup$ As for the reaction mechanism, I would rationalize it as follows: we know that AgX bond is very strong. A transient bond between Ag and Cl readily forms. A "curved arrow" goes from C-Cl to Cl-Ag (charge is transfered from C-Cl to Ag-Cl). At the same time, a curved arrow goes from the Ag-O(H) bond to a new C-O(H) bond, in a sort of internal sn2, being diatomic, fashion with a 4 elements reaction intermediate (C-Cl-Ag-O). The four members cyclic intermediate probably could favor a syn attack, with no stereochemical inversion. $\endgroup$ – The_Vinz Apr 22 '18 at 17:17
  • $\begingroup$ @The_Vinz Thanks, it looks very similar to my proposed one. $\endgroup$ – Archer Apr 22 '18 at 17:20
  • $\begingroup$ This would be reasonable if there were actually reacting AgOH molecules. In such molecule coordination number of Ag is too low. $\endgroup$ – Mithoron Apr 22 '18 at 21:22

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