Aromatic Fluorine as a Chemical Label for Detecting Reaction Mechanism

This article explains how nucleophilically activated fluorine can be used for the detection of ion‐pair formation during the decomposition of various aryl radical generators. Thus a concurrent dual mechanism for the breakdown of certain aryl radical sources can be experimentally demonstrated by fluorine labeling. The bearing of this information on the mechanism of diazo coupling is also discussed. In addition, labeling with aromatic fluorine is applied to the thermolysis of aryl azides, the aminolysis of 3‐aryl‐4‐bromosydnones, and the hydrolysis of 3‐arylsydnone imines. Finally some mechanistic problems are posed which may possibly be solved by this labeling technique.