Studies in Organic Mass Spectrometry III 1, 3‐Cyclohexanediones

The mass spectra of 1, 3‐cyclohexanedione and its 2, 4 and 5 substituted derivatives are discussed. Most fragmentation patterns can be rationalised starting from the diketo form, through initial 1.2 and 1.6 bond cleavages. Evidence is advanced that ionised enol‐molecules mainly yield retro Diels‐Alder type degradations. Ring bond cleavage processes are strongly dependent on the position and size of the substituents.