Ion-Molecule Reactions of 2-Methoxyethanol with Ketones, Aldehydes, Alcohols and Phenols under Chemical Ionization Conditions

Abstract

2-Methoxyethanol has been used as a chemical ionization (CI) reagent gas in a conventional ion source and it has been found to produce numerous reagent ions, including an ion at m/z 89, [CH 3 OCH 2 CH 2 OCH 2 ] + . These ions react with different classes of compounds, e.g. by formation of variety of adduct ions. Neutral ketones (RC(O)R') were observed to yield without exception [M - R + 44] + and/or [M - R'+ 44] + product ions. Similarly, for aldehydes the formation of the product ion [M - H + 44] + is common. Selectivity was noticed especially for the neutral alcohols studied, which resulted in the formation of [M + 27] + and [M + 89] + product ions, and also for the neutral phenols studied, which resulted in the formation of [M + 13] + , [M + 27] + and [M + 89] + product ions. There is a clear correlation between the structure of isomeric neutral alcohols studied and the abundances of the product ion [M + 89] + ; the more hindered the alcohol, the lower is the abundance of the [M + 89] + ion. The [M + 13] + product ion for phenols is a characteristic fragment of the [M + 89] + ion produced by elimination of neutral 2-methoxyethanol. The greatest abundance of the [M + 13] + ion for m-cresol and the use of labelled compounds and labelled reagent gases, CD 3 OCH 2 CH 2 OH and CH 3 OCH 2 CH 2 OD, suggest that the addition occurs mainly to the aromatic ring, ortho and para positions being more favoured. The collision-induced dissociation technique was used to characterize the structures of the product ions