An Introduction to the Chemistry of Carbon-centred Radicals

Most stable ground-state molecules contain closed-shell electron configurations with a completely filled valence shell in which all molecular orbitals are doubly occupied or empty. Radicals, on the other hand, have an odd number of electrons and are therefore paramagnetic species. Electron paramagnetic resonance (EPR), sometimes called electron spin resonance (ESR), is a spectroscopic technique used to study species with one or more unpaired electrons, such as those found in free radicals, triplets (in the solid phase) and some inorganic complexes of transition-metal ions. 

Free-radical chemistry is important in organic photochemistry as, generally speaking, all organic photochemical reactions of in, ) or 3(n,tt ) excited states and all reactions of 3(tt,Jt ) excited states result in the formation of either a pair of radicals or a biradical. We shall consider 

In the gas phase, this decarbonylation reaction is very efficient. Radical rearrangements, which are also possible if the change leads to a more stable product  

The overall process occurring in the above reactions is one of intramolecular hydrogen abstraction. 

Note that the disproportionation reaction involves intermolecu-lar hydrogen abstraction. Due to steric factors, tertiary alkyl radicals undergo disproportionation rather than radical combination. Radicals forming addition products with compounds containing C=C bonds  

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