Carbon compounds average oxidation state

To calculate how many electrons have to be transferred to 02 or NOj respectively, when oxidizing 1 mole of toluene (C7H8) to C02, determine first the average oxidation state of the carbon atoms present in toluene (see also examples discussed in Illustrative Example 2.1). Since this compound is made up only of carbon and hydrogen atoms (the oxidation state of H is +1), you can just consider the hydrogen/ carbon ratio, which yields an average carbon oxidation state of -8/7. Considering that the oxidation state of carbon in C02 is +IV, it is easy to see that a total of (4 - (-8/7)) x 7 = 36 moles of electrons have to be transferred. The overall reactions are, therefore ... 

Because of the importance of carbonyl groups to the mechanism of condensation reactions, much of the assembly of either straight-chain or branched-carbon skeletons takes place between compounds in which the average oxidation state of the carbon atoms is similar to that in carbohydrates (or in formaldehyde, H2CO). The diversity of chemical reactions possible with compounds at this state of oxidation is a maximum, a fact that may explain why carbohydrates and closely related substances are major biosynthetic precursors and why the average state of oxidation of the carbon in... 

Figure 17-13 Some biochemical compounds arranged in order of average oxidation state of the carbon atoms and by carbon-chain lengths. Black horizontal arrows mark some biological interconversions among compounds with the same chain length, while green lines show changes in chain length and are often accompanied by decarboxylation.

If hydrogen, oxygen, nitrogen, and sulfur are assumed to have oxidation states of 4-1, —2, —3, and —2, respectively, it is readily shown that the average oxidation state of carbon in a pure organic compound or a complex mixture such as DOM is... 

The six C3 skeletons shown in Figure 17.9 all have an average oxidation number of-1.33 of their C atoms (i.e, overall oxidation state of all carbon atoms is -4). Accordingly, all these compounds are representatives of the same oxidation state. 

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