Spectrométrie de Masse de Pyrazoline‐5‐Ones N1 Substituées. II. 2‐Pyrazoline‐5‐Ones A Structure Fixe et Pyrazoline‐5‐ones Tautomérisables.

Abstract
The behaviour under electron impact of fixed 2‐pyrazolin‐5‐ones has been investigated. The main decomposition pathway of these compounds is characteristic of their isomeric structure. The fragmentation pattern of tautomeric N1. substituted pyrazolin‐5‐ones must be interpreted in term of CH form; this suggest that this form prevailes in the gas phase. This result has been verified by I. R. for 1,3‐ and 1,4‐dimethylpyrazolin‐5‐one.