Talk:Disproportionation

May 2006

These are synonyms, like covalent bonds and molecular bonds. Kr5t 05:19, 22 May 2006 (UTC)

Sept 2012

Could somebody say why Disproportionation happens, the thermodynamic and other arguments for it?188.28.235.123 (talk) 09:18, 11 September 2012 (UTC)

Well that is a difficult question. First of all, as a percentage of chemical reactions, real disproportionations are fairly rare, so don't get hung up on them. Second, the process describes a stoichiometric relationship, not a pathway or energetic rationale. Third, the reasoning depends on the example. The reactant that undergo disproportionation can be often rather robust (e.g., VCl₃ is a "happy compound," but it disproportionates upon heating:

2 VCl₃ → VCl₄ + VCl₂

This disproportionation is somewhat favored because VCl₄ is volatile and removed from the equilibrium mixture, leaving a residue of VCl₂. In the case of aluminium monochloride, disproportionation starts at very low temperatures (liquid N₂?):

3 AlCl → 2 Al + AlCl₃

Using circular logic, disproportionations occur because the products are more stable than the reactants. Why are the products more stable? That depends on the usual but complex considerations of bond strengths. More common are comproportionation reactions, and you can ask the very same question about why these reactions occur. --Smokefoot (talk) 17:19, 11 September 2012 (UTC)

Disproportionation of acetic acid

How is this disproportionation? H₃CCO₂H -> CH₄ + CO₂

It's a decarboxylation. One molecule is splitting in half. I don't see how this is disproportionation. Pelirojopajaro (talk) 17:48, 4 June 2013 (UTC)

Some people view organic compounds in terms of the oxidation state of carbon. In that sense, CO₂ has C⁴⁺ and CH₄ has C^4-. Acetic acid would be C^3- bonded to C³⁺. Not my idea of disproportionation, but others see it that way, I think. --Smokefoot (talk) 18:08, 4 June 2013 (UTC)

That's silly. Are there any citations where this definition is used? It would kind of make sense if there were two of the same functional group. Pelirojopajaro (talk) 19:45, 4 June 2013 (UTC)

Disproportionation reactions without sources or need checking

• 2CuF → Cu + CuF₂ [1]
• 2CuF₂ → 2CuF + F₂ 2CuF → CuF₂ + Cu [2]
• 2 PtF₅ → PtF₆ + PtF₄ [3]
• Solid TlCl3 is unstable and disproportionates at 40 °C, losing chlorine to give TlCl [4]
• Thallium(III) bromide is unstable and disproportionates at less than 40 °C to TlBr2. [5]
• Tungsten tetrafluoride disproportionates to tungsten and tungsten hexafluoride. [6]
• Molybdenum(V) fluoride disproportionates to tetra and hexafluoride. [7]
• Niobium(IV) fluoride is stable between 275 °C and 325 °C when heated in a vacuum. However, it disproportionates at 350 °C rapidly to form niobium(V) fluoride and niobium(III) fluoride:

$\mathrm {\ 2NbF_{4}\rightarrow NbF_{5}+NbF_{3}}$ (at 350 °C) [8]

• Vanadium tetrafluoride disproportionates to tri and pentafluoride at 325 °C:

2 VF₄ → VF₃ + VF₅ [9] [10] [11] [12]

-- Ktsquare (talk) 20:40, 18 October 2020 (UTC)

• Europium(II) fluoride can be produced by reducing europium(III) fluoride with metallic europium

$\mathrm {2\ EuF_{3}+Eu\longrightarrow 3\ EuF_{2}}$[13]

Reaction-Scope

This article defines disproportionation as being within the scope of redox rections, essentially:

2 X^a → X^a+b + X^a–b

There's currently a content concern about whether that includes how strictly-formal oxidation state analysis to consider. One of the examples of concern there is more of a ligand-exchange in simple covalent clusters, such as:

2 SiHCl₃ → SiCl₄ + SiH₂Cl₂

where it is not clear that some chemists would consider this a redox change (though it does meet the formal definition based on oxidation-statate analysis). However, IUPAC takes an even broader view, with the first of its two definitions not even requiring redox at all in the scope of organic reactions, merely:

A + A → A′ + A″

References

By that, not only does the silicon case fit, but even the autodissociation of water (into hydronium+hydroxide) would be included. That would also surely include the ligand-exchange example. Let's solve the scope first, then decide if there are corner cases. DMacks (talk) 02:24, 22 October 2020 (UTC)