Oxidation of Carbon atom in Alkene, Alkyne and Alkanes of functional groups?
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.