A question in an exam listed a number of compounds and the task was to find the number of compounds which will undergo disproportionation in conc. $\ce{NaOH}$. One of the compounds was $\ce{CCl3CHO}$, which will undergo haloform to give $\ce{CHCl3}$ and $\ce{HCOO-}$. Since one of the carbons is getting reduced and the other is getting oxidized, I considered it to be undergoing disproportionation. According to this answer, as long as the same element gets oxidized/reduced, it is disproportionation; over here, the same element, carbon is getting oxidized/reduced, hence I think it is disproportionation, but the answer says otherwise.

It is impossible for the same atom to get oxidized and reduced at the same time, like for example $\ce{P4}$ in $\ce{NaOH}$, obviously not the exact same atom is getting oxidized and reduced; but the difference between $\ce{P4}$ and $\ce{CCl3CHO}$ is that the phosphorous atoms which are getting reduced are indistinguishable from the ones which are getting oxidized, which is not the case in $\ce{CCl3CHO}$.

So is $\ce{CCl3CHO}$ in conc. $\ce{NaOH}$ considered to be disproportionation or not?

  • 4
    $\begingroup$ Canizzaro is disproportionation, this isn't. To some extent, you even answered why. BTW I'm unimpressed by your exam question, concept of disproportionation is largely useless, especially in organic chemistry. $\endgroup$
    – Mithoron
    Apr 19, 2022 at 16:28
  • $\begingroup$ And chemistry.stackexchange.com/questions/27368/… $\endgroup$ Apr 20, 2022 at 1:51