[eggles]

Can someone help me figure out the mechanism for this reaction? im at my wits end trying to pin it down
the compound is refluxed in water for half an hour with metallic zinc and 20% NaOH leading to deiodination in what i believe is a substitution reaction. i cant give the full structure  but the rest of the molecule shouldnt affect the reaction other than making it very soluble in water

[Dan]

I don't believe that this reaction is catalytic in Zn, it looks stoichiometric to me. The reaction may proceed by oxidative addition of Ar-I to Zn(0), giving an organozinc ArZnI. The C-Zn bond is then hydrolysed (similar to Grignard reagents in water).

Overall: ArI + Zn + H₂O Ar-H + Zn²⁺ + I^- + HO^-

That said, I guess this could also proceed by some kind of single electron transfer mechanism, but I'm no expert in that area.

[Honclbrif]

I'm also pretty sure its analogous to Grignard hydrolysis. Since organo-zinc is usually* pretty unreactive it does not give you any trouble with the amides.

The NaOH is probably there to clean off the surface of the metal and keep the Zn salts soluble.

*Ok, diethyl zinc is a classic fire starter, but R-Zn-X usually pretty tame

[eggles]

i think you right.the iodide content is measured using a complexometric titration with AgNO₃ to for AgI after the the sample is reacted filtered so maybe the OH^- is there to precipitate out the Zn²⁺ as ZnOH₂ so it doesnt form any complexes that would give false results?