Question

How do we determine carbon oxidation numbers in organic molecules?

Answer 1

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.