Organic Chemistry II

Professor Carl C. Wamser

Chem 335 - Winter Term

Organic Redox Reactions

You may balance organic redox reactions in the usual manner using oxidation numbers and electron transfers (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 ):