Green Chemistry and the Ten Commandments

Chap. 11. Toward a Greener Anthrosphere through Industrial Ecology 299

and at the anode where electrons are removed, O 2 is released as the water is oxidized:

2H 2 O → O 2 + 4H+ + 4e- (11.9.2)

In the setup shown, H+ ion generated at the anode would eventually contact OH

-

ion
generated at the anode, and the two would react to produce water again. At the cathode,
a dissolved chemical species could be reduced directly or the hydrogen generated could
add to a species, reducing it. And at the anode another species could be oxidized directly
by loss of electrons or the oxygen generated could add to a species, oxidizing it.

2H 2 O → O 2 + 4H+ + 4e-

+ -

Battery

Cathode Anode

H 2 O,

dissolved   salt

2H 2 O + 2e- → H 2 + 2OH-

Figure 11.3. Apparatus for electrolysis in which a direct current of electricity is passed through a reaction
medium, in this case water with a dissolved salt to make it electrically conducting. Reduction occurs when
electrons are added to the medium at the cathode and oxidation when they are removed at the anode.
Electrolysis is a reagentless way of doing oxidation and reduction.

As another example of a commonly performed reaction that normally requires
potentially troublesome reagents, consider alkylation with alkylating reagents in which
an alkyl group, most frequently the -CH 3 (methyl) group, is added to an atom on an
organic compound. The methylation reaction,

H

R N

CH 3

H 3 C O S CH 3

O

O

O

H

N

H

2 R + +­­2NaOH

2 +­­Na 2 SO 4 ­­+­­2H 2 O (11.9.3)

shows attachment of a methyl group to an amine group, -NH 2 , that is part of an unspecified
molecule represented “R.” Methylation of nitrogen is used in a number of chemical