O(-) and OH(-) react with fatty acid methyl esters (FAMES) under chemical ionization conditions both as Bronsted bases to form [M - H](-) and as nucleophiles to form the carboxylate ion RCOO(-). O(-) shows a much greater tendency to react as a nucleophile than does OH(-). The [M - H](-) ions fragment by elimination of CH(3)OH, with unsaturation in certain positions in the fatty acid hydrocarbon chain promoting this elimination for unknown reasons. The reaction of O(-) and OH(-) with triacylglycerols leads to [M - H](-), characteristic of the molecular mass, and to carboxylate ions characteristic of the fatty acid(s) present in the lipid. The presence of the three ester functions in the lipids greatly enhances the formation of carboxylate ions compared to the FAMES.

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The CH: adducts of benzaldehyde, acetophenone, propiophenone and butyrophenone were prepared using CH,F-CH, and CH,CI-CH, mixtures under chemical ionization conditions and the unimolecular and collisioninduced fragmentation reactions of their adduct ions were studied. For comparison, the fragmentation reactions of the protonated pmethylpbenyl alkyl ketones were studied as models of the ring-methylated species and the fragmentation reactions of [ C,H,C(R)=OCH,] +, produced by electron impact ionization of the appropriate methyl ether, were studied as models of the O-methylated species. From these comparisons it is concluded that methyl cation addition occurs predominantly at the carbonyl oxygen under our experimental conditions. However, for methyl-cationated acetophenone there is extensive migration of the methyl group from the oxygen to the ring prior to fragmentation of the adduct.