C-H, alkane

One of the most popular nitroxide-based radicals (TEMPO) has been shown to abstract H-atoms from activated C—H bonds. However, the nitroxide itself is easily photo-degraded, hi order to examine more photochemically stable alternatives to TEMPO in abstraction reactions, the related isoindoline nitroxide radical (61) has been examined.116 Abstractions from unactivated primary, secondary, and tertiary C—H alkane bonds were all achieved. 

From the i.r. readout, the characteristic C-H alkane absorption is present at 2800 cm . The sharp, symmetric absorption at 1380 cm indicates the presence of either i methyl or ethyl but not an isopropyl or t-butyl group. 

As a result of Lewis centre attack on the C-H alkane bond a pentaco-ordinated transition-state complex is formed. 

We have looked at the nature of the double bond found in the hydrocarbons called alkenes on pages 193-4. Alkenes with one double bond per molecule have the general formula C H. One example is ethene, C H. Alkanes are described as saturated hydrocarbons however, alkenes are described as unsaturated hydrocarbons. 

---