Upon treatment with Tollens' reagent (ammoniacal silver(I) nitrate), aldehydes are oxidised to carboxylic acid, and silver(I) is reduced to silver metal.
I am trying to find a mechanism for the this reaction online, but the only thing I can find is the balanced equation. Can someone propose or help me find the mechanism?
Answer
Here are the two half reactions:
[Ag(NHX3)X2]X++eX−⟶AgX0+2NHX3RCHO+3OHX−⟶RCOX2X−+2HX2O+2eX−
which together yield the overall reaction
2[Ag(NHX3)X2]X++RCHO+3OHX−⟶2AgX0+RCOX2X−+4NHX3+2HX2O
Here is a diagram of the reaction mechanism. The carbonyl group is oxidized in the process and the AgX+ is reduced. The resultant oxidized aldehyde (now a radical cation) reacts with hydroxide to form a tetrahedral intermediate. A gem-diol like intermediate is formed via a hydrogen shift, which then continues on to the final carboxylate anion.
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