The importance of mesomerism in the termination of alpha-carboxymethyl radicals from aqueous malonic and acetic acids.

In the dioxygen-free aqueous malonic and acetic acid systems, alpha -carboxymethyl radicals are produced through hydrogen abstraction from the parent compound by radiolytically generated OH radicals. H abstraction from the CO2-/ CO2H group followed by decarboxylation is a process of small importance (less than or equal to5%). The alpha -carboxymethyl radicals terminate by recombination. Two types of recombination product are observed which are characterised by the formation of a C-C linkage or a C-O linkage. alpha -Carboxymethyl radicals are mesomeric systems, Their mesomeric state depends on the state of protonation and determines the proportion of the C-C- versus C-O-linked dehydrodimers they produce.