Sentence:  As suggested by Weinmayr in this example, the reaction proceeds by a different mechanism, not with the formation of free radicals but rather with separation of the C — Hg bond, thus producing <WSD>pseudoradicals</WSD> which do not diffuse into the reaction medium. 
Meaning of the word marked with <WSD> tags:  An atom or group within a molecule which behaves like a free radical due to high valence.