Oxidative Additions: Don't Get How Metal Oxidizes?

[CrimpJiggler]

I don't get how oxidative additions "oxidize" the metal. For example, methyl chloride. Let's say the chloride anion donates 2 electrons to form a bond with the metal. The metal gains 2 new electrons so this is a reduction isn't it? The metals oxidation state should increase by 2. The methyl cation will also form a bond using two of the electrons from the metal atoms oxidation state should go down 2 again. I don't see how the metals oxidation state increases by 2.

 

[bm0p700f]

When oxygen reacts with something like a metal the oxygen atom gains two electrons and the metal loses two (e.g. Cu). Copper is oxidised as it loses electrons.

Reducesing is the opposite. The metal gaining electron would be reduction. Hense Carbon is know as a reducing agent for many metal oxides as the metal atoms gain electrons to form a metal solid.

That is how oxidation and reduction are defined.

 

[CrimpJiggler]

Thanks, I learned a couple of things from your reply. It didn't answer my question though. I've figured out the answer to the question though. Using an oxidative addition of HCl as an example, the Cl- anion adds to the metal and since the Cl- donated both electrons, the oxidation state doesn't change. It didn't reduce the metal there though because Cl is far more electronegative than the metal and if the Cl leaves, its taking both electrons with it. The H+ counterion must now add to the metal and since it has no electrons, it takes 2 electrons from the metal to form the new bond. Hence, the oxidation state of the metal increases by 2.

What you said there got me thinking. You said carbon reduces the metal atom in metal oxides. The metal atom is less electronegative than carbon though. Therefore, is it only because carbon forms a stable gas with oxygen that this happens? In other words, the reaction would be in an equilibrium which favors the metal oxide but the product of the reaction between carbon and oxygen, since its a gas, leaves the reaction site as soon as its formed.

 

[bm0p700f]

Electronegivity difference is a tool for telling you hove ionic or covelent a bond is. It also can be used to decide where the partial charge in a molecule resides if the bonds are polar. I would use it for more than that. Carbon reduces metals below itself in the reactivity series. I donlt think it has much to with electronegitivity.