Oxidation/Reduction Orgo Confusion

[darkhope]

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Hi guys
So I'm looking at the kaplan prep and it says that adding bonds to hydrogen is reduction and adding bonds to oxygen is oxidation. I'm so confused on why that is? Because how does a carbon bonding to a hydrogen lower the oxidation number of the carbon? And how does a carbon bonding to an oxygen increase the oxidation number of the carbon?
Thanks

 

[ruchir]

When you add a more electronegative atom (oxygen) it "hogs" the electrons, therefore carbon assumes an oxidative state. Vice-versa for hydrogen.

 

[deleted329605]

So if you look at electronegativity values, you see carbon has a slightly stronger pull on electrons through a covalent bond than does hydrogen. The opposite is true for carbon next to oxygen, with O taking most of the electron density. Therefore, Carbon gets reduced (takes on a smaller + charge) when next to more hydrogens, and gains a + charge when next to the more electronegative oxygen atom. Therefore when you take an alcohol say primary alcohol and use an oxidizing agent like KMnO4 which itself has a large positive charge, the oxygen gains a more positive charge by being exposed to more oxygen in becoming a carboxylic acid and the oxidizing agent, the KMnO4 because another manganese oxide but with a lower oxidation number.

 

[darkhope]

Thanks alot guys!!!