Tbe collision-induced dissociation mass-analysed ion kiwtic energy (CID MIKE) spectra (electron impact and chemical ionization) of five adia~arykulpbonylaminoalkan-2~nes and corresponding N-arylsulpboaylazetidin-3-0and N-arylsulpboaylpyrrolidio-3-uiws were studied. The IM -Nzl*' and IMH -NzI + ioas of two types of tbe diazo ketows provide CID MIKE spectra similar to those of the corresponding M" and MH' of tbe heterocyclic compounds, i.e a cyclization analogous to that in solution takes place. For the otber three types of diazo compoumls the Wolff rearrangement prevails in both the gas and liquid phases. The eftect of the substitwnts on the cyclization process was studied The data obtained permit the results of acid-catalysed cyclizptioa of similar diazo ketones to be predicted on the basis of tbeir CID MIKE spectra. Chemical ionization provides a closer similarity with reactioas in solution than electron impact ionization, which can be rationalized by tbe protonation of the diazo Letow molecule being the driving force of the cyclization reaction either in solution or in the ion source of a mass spectrometer.

+ E spectra derived from the molecular anions of flavones and quinones are used to illustrate and compare the resolution and sensitivity of spectra obtained by both magnetic and electric sector scan techniques. Some fragmentations are noted which do not occur in the conventional positive-ion spectra of these compounds.

α-Dicarbonyl compounds form stable parent negative ions by capture of low-energy electrons. The parent negative ions undergo a variety of collision induced dissociations, the most characteristic being β cleavage to a carbonyl group, i.e. see diagram in paperCyclic α-dicarbonyl parent negative ions may also eliminate molecules of carbon monoxide, for example the fragmentations M- → [M-(R + CO)]- M- →[M - (R-2CO)]- and M- → [M-2CO]- occur in a number of cases.

Kinetic energy release values [T(50%) values] between 0.05 and 0.8 eV have been noted for the unimolecular decomposition M- → (M-NO.)- of the molecular anions of variously substituted nitrobenzenes. Large T values are observed when the substituent is strongly electron-withdrawing. Composite peaks are obtained for m-nitrobenzoic acid and m-nitroacetophenone, showing the occurrence of two distinct processes in these cases.

Under electron ionization conditions, the ortho-substituted Schiff bases N-benzylidene-o-toluidine (1a), N-(o-methylbenzylidene)aniline (1b), N-salicylideneaniline (1c) and N-(o-methoxybenzylidene)aniline (1d) give fragment ions which have been shown by collision-activated mass-analysed ion kinetic energy spectra to have the structure of the protonated molecular ions of indole (2), benzofuran (3), and 1,2-benzisoxazole (4). The molecular ion of N-(o-methylbenzylidene)-o-toluidine (1f) gives as fragment ions not only the protonated molecular ion (2) of indole and the tropylium ion but also the molecular ion of anthracene. Attempts to find supporting evidence for a mechanism for this rearrangement by deuterium labelling of a methyl group in (1b), such as (1g), have been unsuccessful.