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Nomenclature priorities are in order of the degree of oxidation of the carbon atom.

I am not sure if it's advisable to just take it as it is and use it or try to understand the basis of the functional group prioritization. I guess the latter interest me. So looking at the priorities for functional groups,

Alkene has higher priority than Alkyne and followed by Alkane. I started reading some materials about Oxidative Cleavage of Double Bonds and rest of the reactions, which kinda went way over my head.

Can someone explain, how and why the carbon oxidation in Alkynes are lower than Alknenes? Or put in another word, why would Alkene carbon oxidate faster than Alknenes?

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  • $\begingroup$ @bon why did you remove the functional group and hydrocarbon tag? Just curious to know. $\endgroup$
    – bonCodigo
    Commented Jul 2, 2015 at 10:26
  • $\begingroup$ @Have a look at the meta post about functional group tags. $\endgroup$
    – bon
    Commented Jul 2, 2015 at 10:28
  • $\begingroup$ There are two separate questions in the last paragraph. They are not the same question and I think the first is the one which is relevant to the rest of the post. $\endgroup$
    – bon
    Commented Jul 2, 2015 at 11:09

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Nomenclature priorities are in order of the degree of oxidation of the carbon atom.

This may be true for the heteroatom functional groups, but not for alkenes, alkynes, and alkanes.

Consider that each $\ce{C-H}$ bond contributes $-1$ to the oxidation state and each $\ce{C-C}$ bon regardless of order contributes $0$ to the oxidation state of carbon.

Thus:

hydrocarbon   formula   functional group   oxidation number of C
ethane        CH3CH3    alkane             -3
ethene        CH2CH2    alkene             -2
ethyne        CHCH      alkyne             -1

Alkynes have a higher oxidation number than alkenes.

Alkenes react better in oxidation reactions than alkynes because alkenes are less oxidized than alkynes.

The organic chemistry textbook that I teach from explains that alkenes have higher nomenclature priority than alkynes because alkenes are more common. I cannot find a more authoritative reason/source.

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  • $\begingroup$ The question that drives me a little confusing is, the order is: alkene, alkyne and alkane... so from the perspective of single, double, tripple bond, I really do not see an order at all... You have stated because alkenes are less oxidized than alkynes. Well how important to understand the underlying oxidation theory of these guys, from biochemistry and pharmacology aspect? $\endgroup$
    – bonCodigo
    Commented Jul 2, 2015 at 15:08

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