Studies in mass spectrometry. Part XXIII. The mass spectra of dimethyl esters: methoxy-migrations in the mass spectra of dimethyl esters

Abstract

A series of saturated linear dimethyl diesters [MeO₂C·[CH₂]_n·CO₂Me, n= 1–8 or 12], hitherto only examined by low resolution mass spectroscopy, have been examined using a high resolution instrument. An important decomposition mode for M– CO₂Me and M– CH₂CO₂Me ions is loss of keten with associated methoxy-migration. In this manner, ions with compositions corresponding to those normally derived from saturated aliphatic ether groupings are generated. Carbonium ion-stabilising substitutents in substituted dimethyl succinates and glutarates in general enhance the abundance of the rearrangement ions, which frequently are among the most abundant in the spectra.