Here is a diagram of the reaction mechanism. The carbonyl group is oxidized in the process and the $\ce{Ag^+}$ 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.
Here is a diagram of the reaction mechanism. The carbonyl group is oxidized in the process and the $\ce{Ag^+}$ 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.
@GaurangTandon Your question is quite different from the original question so you might want to post it as a new question. My view would be that since a typical alcohol does not have a readily available electron (e.g. high-lying HOMO as a carbonyl has), an alcohol would not undergo 1 electron oxidation and react with Tollens reagent in a normal fashion to produce the characteristic silver mirror. That said, if you heat things up, or have oxidizing impurities in the sample, then all bets are off and anything could happen.More
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A Google search for "Tollens' test mechanism" gave me a link to this article: J. Chem. Res.2011,35 (12), 675–677. A quick glance at the text of the article leads to the conclusion that the currently proposed mechanism is as follows:
However, it seems that there is no direct evidence for these exact mechanisms, though they seem believable. That is normal, though; proving any mechanism is a long and tedious task that can take decades of dedicated studies, so we have to live with it.
A Google search for "Tollens' test mechanism" gave me a link to this article: J. Chem. Res.2011,35 (12), 675–677. A quick glance at the text of the article leads to the conclusion that the currently proposed mechanism is as follows:
However, it seems that there is no direct evidence for these exact mechanisms, though they seem believable. That is normal, though; proving any mechanism is a long and tedious task that can take decades of dedicated studies, so we have to live with it.
I couldnt see any mechanism or text describing the mechanism on the link you provided, you could? Also, your mechanism suggests that silver(I) will oxidize saturated carbons containing a hydrogen, for example, dimethoxymethane. Is this reported in the literature?More
1) You have to download and read the article for it. 2.a) It was reported that aldehydes forming stable hydrates, like $\ce{CCl3CHO}$, reacts much faster. 2.b) Tollen reagent does give false positive, but I am too lazy to find full list.More
Here are the two half reactions:
$$\begin{align} \ce{[Ag(NH3)2]+ + e- &-> Ag^0 + 2NH3} \\ \ce{RCHO + 3OH- &-> RCO2- + 2H2O + 2e-} \end{align}$$
which together yield the overall reaction
$$\ce{2[Ag(NH3)2]+ + RCHO + 3OH- -> 2Ag^0 + RCO2- + 4NH3 + 2H2O}$$
Here is a diagram of the reaction mechanism. The carbonyl group is oxidized in the process and the $\ce{Ag^+}$ 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.
Here are the two half reactions:
$$\begin{align}\ce{[Ag(NH3)2]+ + e- &-> Ag^0 + 2NH3} \\\ce{RCHO + 3OH- &-> RCO2- + 2H2O + 2e-}\end{align}$$
which together yield the overall reaction
$$\ce{2[Ag(NH3)2]+ + RCHO + 3OH- -> 2Ag^0 + RCO2- + 4NH3 + 2H2O}$$
Here is a diagram of the reaction mechanism. The carbonyl group is oxidized in the process and the $\ce{Ag^+}$ 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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A Google search for "Tollens' test mechanism" gave me a link to this article: J. Chem. Res. 2011, 35 (12), 675–677. A quick glance at the text of the article leads to the conclusion that the currently proposed mechanism is as follows:
$$\begin{align} \ce{R-CHO + H2O &-> R-CH(OH)2} \\ \ce{R-CH(OH)2 + Ag+ &-> R-C^.(OH)2 + H+ + Ag^0} \\ \ce{R-C^.(OH)2 + Ag+ &-> R-COOH + H+ + Ag^0} \end{align}$$
In strongly alkaline solution (pH > 10) the mechanism changes to the following:
$$\begin{align} \ce{R-CHO + OH &-> R-CH(OH)O-} \\ \ce{R-CH(OH)O- + Ag+ + OH- &-> R-C^.(OH)O- + H2O + Ag^0} \\ \ce{R-C^.(OH)O- + Ag+ + OH- &-> R-COO- + H2O + Ag^0} \end{align}$$
However, it seems that there is no direct evidence for these exact mechanisms, though they seem believable. That is normal, though; proving any mechanism is a long and tedious task that can take decades of dedicated studies, so we have to live with it.
A Google search for "Tollens' test mechanism" gave me a link to this article: J. Chem. Res. 2011, 35 (12), 675–677. A quick glance at the text of the article leads to the conclusion that the currently proposed mechanism is as follows:
$$\begin{align}\ce{R-CHO + H2O &-> R-CH(OH)2} \\\ce{R-CH(OH)2 + Ag+ &-> R-C^.(OH)2 + H+ + Ag^0} \\\ce{R-C^.(OH)2 + Ag+ &-> R-COOH + H+ + Ag^0}\end{align}$$
In strongly alkaline solution (pH > 10) the mechanism changes to the following:
$$\begin{align}\ce{R-CHO + OH &-> R-CH(OH)O-} \\\ce{R-CH(OH)O- + Ag+ + OH- &-> R-C^.(OH)O- + H2O + Ag^0} \\\ce{R-C^.(OH)O- + Ag+ + OH- &-> R-COO- + H2O + Ag^0}\end{align}$$
However, it seems that there is no direct evidence for these exact mechanisms, though they seem believable. That is normal, though; proving any mechanism is a long and tedious task that can take decades of dedicated studies, so we have to live with it.
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