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Oxidation and Reduction

Oxidation: Reduction:

Calculating Oxidation Number or State (there are several methods for doing this, pick the one that works for you !)
This allows for a more formal, quantitative decription of the oxidation state and is based on looking at the relative electronegativity of the atoms attached to the atom being assessed. The algebraic sum of the oxidation states must equal the charge of the molecule.

If we are looking at a central carbon atom:

If we are looking at a generic central atom

Here are a few examples, and a couple of schemes that show important relationships:

Calculating oxidation state
Oxidation state and Redox relationship of Hydrocarbons
Oxidation state and Redox relationship of oxygen functional groups

Study Tip:
In the past you may have learnt that O is always -2, however it is better to count each bond to an O as -1 since there is a difference between C=O and C-O as seen by comparing the aldehyde and the alcohol in the diagram above. After all , the -2 statement is wrong.... e.g. in oxygen gas, O2, the oxidation state is zero


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organic chemistry © Dr. Ian Hunt, Department of Chemistry University of Calgary