Chemistry Reference
In-Depth Information
radical. The least stable alkyl radical is the methyl radical, which has no
alkyl substituents and therefore no mechanism whereby the unpaired
electron can be stabilised:
CH
.
Radicals in which the lone electron can be distributed around the
molecule by resonance effects are particularly stable and occur in a number
of oxidative reaction mechanisms. Examples of comparatively stable
radicals of this type are the benzyl free radical and free radicals containing
the allyl (or propenyl) group. These species can be stabilised as shown in
Figure 8.5.
3
2
1
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
CH
2
CH
2
CH
CH
2
Figure 8.5
The stability of allyl and benzyl radicals.
Drugs that are susceptible to oxidation of carbon-hydrogen bonds
include ethers (which oxidise to form highly explosive peroxides), aliphatic
amines (which oxidise at the a hydrogen atom) and aldehydes (which are
easily oxidised to carboxylic acids and peroxy acids). Examples of these
reactions are shown in Figure 8.6.
Other bonds that oxidise easily are the oxygen-hydrogen bond found
in phenols and the nitrogen-hydrogen bonds found in aromatic amines
(Figure 8.7).
