p-Nitrophenylazo-, o-nitrophenylazo-, and 2,4-dinitrophenylaso derivatives of 9-phenylfluorene and triphenylmethane have been prepared and the kinetics of their decomposition in toluene has been studied. In each case the phenylfluorenyl derivative decomposed more rapidly than the corresponding triphenylmethyl derivative, and with lower activation energy. This is ascribed to and cited as evidence for the greater resonance stabilization of phenylfluorenyl as compared with triphenylmethyl radical. The partially compensating energies and entropies of activation are discussed. The relevance of these results to the dissociation of the related hexaarylethanes is discussed. Attempts to prepare azo compounds as sources of 9-fluorenyl radical, for comparison with diphenylmethyl, are described.

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