Chem 335 - Winter 2002
Organic Chemistry II
Dr. Carl C. Wamser
You may balance organic redox reactions in the usual manner
using oxidation numbers and electron transfers
(see the approach in most general chemistry textbooks)
Oxidation number is calculated assuming polar bonds between different atoms,
where a C-H bond is polarized C-/H+ , a C-O bond is C+/O- , and a C-C bond is nonpolar
Or you may use the following technique, which recognizes that
Many organic oxidation/reduction reactions amount to a change of one O atom or 2 H atoms
( sometimes a generic oxidant is written as [O] or reductant as [H] )
Examples of oxidations (with C oxidation numbers):
Steps in balancing redox reactions:
1) Divide the overall reaction into an oxidation half-reaction and a reduction half-reaction
2) Balance atoms other than O and H by inspection
3) Balance charges by adding, as needed, H+ (in acidic solution) or OH- (in basic solution)
4) Balance O by adding H2O as needed
5) Balance H by adding H (neutral H atoms, an artificial device)
6) Combine the two half-reactions so that the artificial H atoms cancel
7) If desired, add appropriate counterions (e.g., Na+)
Example:
Oxidation half-reaction:
Reduction half-reaction:
Overall reaction ( 3 x oxidation half-reaction + 2 x reduction half-reaction ):
