Abstract
Oxidative Coupling of CH‐acid Compounds with p‐Phenylenediamines. V. Mass Spectrometric Fragmentation of 4‐Substituted 3‐Methyl‐1‐phenyl‐pyrazolin‐5‐onesThe mass spectra of 3‐methyl‐1‐phenyl‐pyrazolin‐5‐one 1 and 4‐substituted derivatives 2–18 have been studied and the fragmentation mechanisms are discussed. The major cleavages take place in three ways, whose significance is related to the properties of the substituents. The mass spectra permit the determination of the structure, purity and stability of the substituted colour couplers.