Loss of CO from the ion of 2,4‐pentanedione

Abstract

Loss of CO from the Molecular Ion of 2,4-PentanedioneZamir et al. ' have proposed the mechanism for loss of CO from the molecular ion of 2,4-pentanedione (acetylacetone), 1, which involves the transfer of one of the two methyl groups to a more remote carbonyl function prior to loss of CO, and the resultant ion is depicted as the molecular ion of methyl isopropenyl ether, 2, (Scheme 1). CH3 J m/z 100 m / z 72 1 2 Scheme 1. Mechanism of CO loss from the molecular ion of 2,4pentanedione proposed by Zamir et a/.' 5.

Methyl Migration in the Metastably Decomposing Acetylphenyl Ions, CH3COC6H4+ (m/z 119), Followed by the Loss of CO

“…6), 7) However, this type of dissociation is scarcely observed in the mass spectra of the compounds, RC 6 H 4 COX, 8) except for the case of X῍ F. 9) This is due to the extreme stability of substituted benzoyl ions, RC 6 H 4 CO ῌ . To explain the loss of CO from ῌ C 6 H 4 C(῍O)OCH 3 ion (m/z 135) generated by the consecutive losses of OCH 3 and CO from the molecular ions of dimethyl phthalate, isophthalate, and terephthalate, we have proposed that OCH 3 migrates from the C(῍O)OCH 3 group to the charge site in the ortho position in the benzene ring or to the incipient charge site.…”

“…The sourcegenerated m/z 147 ions, except for 1, decomposed into only the m/z 119 ion by the loss of CO in the metastable time window. Therefore, the m/z 119 ion, which has the initial structure shown in Scheme 1, will be generated by the consecutive losses of CH 3 and CO from the respective molecular ions. In addition to this reaction, the m/z 147 ions generated from 1 ῌῌ further decompose into three ions at m/z 129, 104, and 91 by the losses of 18 Da, 43 Da, and 56 Da neutral species, respectively, as shown in Fig.…”