How do we determine carbon oxidation numbers in organic molecules?

1 Answer
Aug 19, 2016

Answer:

Usually it is fairly simple, but there are a few tricks to use.

Explanation:

Carbon has oxidation numbers from #-IV# (cf methane, carbon is slightly more electronegative than hydrogen) to #+IV#, as in #CO_2#. But how to determine the oxidation number in other scenarios?

When we assign oxidation numbers, the more electronegative atom gets the electrons; thus #CH_4#, #C^(-IV) + 4xxH^(+I)#, but if we have a #C-C# bond, the electrons are ASSUMED to be shared by each carbon (because they have equal electronegativities). Thus in ethane, we have #C^(-III)#, and in propane, #2xxC^(-III)#, the carbon termini in the chain, and the methylene #CH_2# carbon is #C^(-II)#. Of course these are all oxidized up to #C^(+IV)# upon combustion to give what?

Can you assign oxidation numbers for carbon in butane? What about the oxidation numbers in cyclohexane? Try it, and post the answer back here.