Ionization and Dissociation of Formic Acid, Acetic Acid, Propanoic Acid, and Butanoic Acid under Electron Impact

Abstract

The mass spectra of DCOOD, DCOOH, CD3COOD, CD3COOH, CH3COOD, C2H5COOD, and C3H7COOD are compared with spectra of the H-containing compounds. Besides, the 18O-labeled acetic acid is measured.The labeling helps to determine the origin of a number of fragment ions. It is found that the two fragment ions C3H5O2+ and C4H7O2+ are produced by the removal of the hydrogen atom from the alkyl group and have the structures of C2H4CO2H+ and C3H6CO2H+ respectively.Neither CH2CO2H+ nor CH3CO2+ is produced.The rerrangement ion CH3O+ is found to have the structure of CH2OH+, one of whose hydrogen atoms comes from the carboxyl group.The origins of the hydrogen atom and the oxygen atom in the other rearrangement ions are also determined. The mechanisms for the fragmentation of the molecular ions are discussed.

The electronic structure and deexcitation pathways of an isolated metalloporphyrin ion resolved by metal L-edge spectroscopy

“…Therefore, fragments at m / z 273.1, m / z 264.1 and m / z 252.0 can be unambiguously assigned to charged fragment losses from excited [CoPPIX 3+ ]*. In particular charged carboxylic groups, namely CH 2 CH 2 COOH + (73 u) and CH 3 COOH˙ + (60 u), are known as the main products from electron impact ionisation of long-chain carboxylic acids 71 and could contribute to charged fragment losses from excited [CoPPIX z ≥3+ ]*. With this assumption we assign the fragment series at m / z 273.1, 264.1 and 252.0 to the loss of ccCa + , ccCa + + w and ccCa + + m + v, respectively (see Fig.…”

Mass spectrometry

“…The mass spectrum of 3,4,4-trimethyl-5-oxo-inms-2-hexenoic acid has unusual features (826). The ionization and dissociation of formic acid, acetic acid, propanoic acid, and butanoic acid have been studied using labeling and metastable peaks (327). On the more theoretical side, scission probabilities of skeletal bonds in the mass spectra of alkyl acetates have been deduced (328).…”