Magnetic Field Effects in Free Radical Reactions

3 Magnetic Field Effects in Free Radical Reactions 

The triplet state of the geminate radical pair has three distinct levels (aa, /3/3, a/3 4- /3a) which are isoenergetic in the absence of any magnetic field. They interconvert very rapidly with the isoenergetic singlet state, so that the spin flip is fast and recombination is efficient. 

This magnetic field effect can be used to control to some extent the molecular weight of some polymers formed by free radical initiators. Such initiators undergo homolytic dissociation to form a radical pair A B which attacks the ends of growing polymer chains to add further monomeric units (section 6.2) polymerization ends when the free radicals A and B (or A and A, B and B ) recombine. Assume there are only two radicals (A and B ) in a micelle if one of these escapes from the micelle there can be no 

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