Selectivity of gas‐phase ion/molecule reaction of carbon dioxide with phenide ions

Abstract

On contrary to the widely accepted conviction that the m/z 93 ion derived from phenol does not react with CO2, we demonstrate that it makes an adduct with CO2 to a small but demonstrable extent. For example, the product-ion mass spectrum recorded for the m/z 98 ion derived from [(2)H6]phenol showed a small peak at m/z 142 when CO2 was used as the collision gas. The formation of an m/z 137 adduct ion from the m/z 93 ion (generated either directly from phenol, or indirectly from salicylic acid by in-source decarboxylation) was demonstrated also by multiple-reaction-monitoring tandem mass spectrometric experiments. According to literature, the m/z 93 ion derived from salicylic acid does not undergo CO2 addition because it is deemed to exist only in the phenoxide form. This reaction has been previously proposed as a method for differentiating phenoxide ion from its isomeric hydroxyphenide ions. We propose that the m/z 93 ion, albeit small, exists also as the phenide form together with the predominant phenoxide ion.

Formation of Carbamate Anions by the Gas-phase Reaction of Anilide Ions with CO2

“…To start with, we pursued to find out whether the anilide ion would add to CO 2 in a manner similar to that reported for phenoxide and phenide ions [8,9]. Our preliminary results indicated that the anilide ion undergoes facile addition to CO 2 .…”

“…A ratio calculation after peak integration showed that the relative peak area of the m/z 137 peak was about 3.8 when normalized to that of the m/z 136 peak. Evidently, the anilide ion demonstrates a strong affinity to CO 2 compared with the extremely mediocre affinity shown by the phenoxide ion [9].…”

“…Under standard conditions, the nitrogen gas delivered from the external supply (at 60 psi) is divided to supply the curtain gas and the collision gas (Supplementary Figure 1a). To introduce CO 2 or any other gas as the collision gas, a T-junction and two toggle valves were added at the entrance to the collision cell [9] (Supplementary Figure 1b). To mix an additional gas, another Tjunction was introduced and the gas flows were controlled by needle valves (Supplementary Figure 1c).…”

“…In general, the CO 2 addition reaction has also been proven to be useful as a structural probe for gaseous anions [7][8][9][10][11][12][13][14][15][16]. For example, Bienkowski and Danikiewicz [7] showed that the phenyl anion acts as a nucleophile and reacts with CO 2 in the gas phase to generate the benzoate anion.…”

“…Subsequently, the reaction has been successfully used to derive structural information of carbanions generated by decarboxylation of isomeric hydroxy-and sulfo-benzoic acids [8,17]. Previously, we reported that even the phenoxide anion (m/z 93) adds to CO 2 to a small extent [9].…”