Gas‐phase ion‐molecule reaction of alpha‐phenylvinyl cation towards substituted benzenes in the environment of an ITMS

Abstract

Ion-molecule reactions between the α-phenylvinyl cation (α-PVC) and mono-substituted benzenes have been investigated using a quadrople ion-trap mass spectrometer. The α-PVC, generated by chemical ionization from phenylacetilene, was found to react selectively with mono-substituted benzenes bearing electron withdrawing groups to give the product ions [M + 103](+) and the trans-vinylating product ions [M + 25](+). To characterize the reaction products, a combination of collision-induced dissociation, isotope-labeling experiments and model compounds were used. The results indicate, in addition to direct heteroatom alkylation, high extent of ortho attack. We attributed the positional selectivity of the α-PVC to the nature of the substituent on the neutral molecule. In particular, hydroxy and amino groups promoted the alkenylation at ortho position.

Evaluation of the α‐phenylvinyl cation as a chemical ionization reagent for the differentiation of isomeric substituted phenols in an ITMS

“…Although the CID mass spectra of the reaction products ( m / z 227) from isomeric derivatives 1–3 show two common fragment ions with similar abundances, namely, the reformation of the starting PVC ( m / z 103) and the trans ‐vinylating product ( m / z 149), however, the spectra yield same unique behaviors for individual regioisomers that allowed their differentiation. The meta isomer can be distinguished from the ortho and para isomers because of the formation of a unique ion at m / z 125 (Fig.…”

“…Details on the use of the Saturn ion trap for ion–molecule reaction have been reported previously 1z . The CI parameters for the generation of the CI reagent gas are described in detail elsewhere …”

“…The reaction of α ‐PVC towards the aromatic compounds 1–11 was performed by mass selecting the reagent ion at m / z 103 and storing it inside the IT. Isolation of the m / z 103 ions was achieved by using the standard MS/MS isolation function available via the saturn gc/ms workstation version 5.41 software and keeping the CID energy at 0 V in order to avoid the activation of decomposition processes . Each reaction product, obtained from the reaction of the neutral analyte with the reagent gas, was isolated and then collisionally activated prior to mass analysis.…”

“…1z The CI parameters for the generation of the CI reagent gas are described in detail elsewhere. [14] The reaction of α-PVC towards the aromatic compounds 1-11 was performed by mass selecting the reagent ion at m/z 103 and storing it inside the IT. Isolation of the m/z 103 ions was achieved by using the standard MS/MS isolation function available via the SATURN GC/MS WORKSTATION version 5.41 software and keeping the CID energy at 0 V in order to avoid the activation of decomposition processes.…”

Conversion of benzoic acid into phenol in an ITMS under CI‐MSn conditions. Recognition of ortho‐chlorobenzoyl derivatives

“…CI‐specific parameters used for methanol as reagent gas were automatic gain control prescan ionization time 200 μs, CI maximum ionization time 2000 μs, CI maximum reaction time 40 ms, CI reagent ion eject amplitude 15.0 V, CI storage level 19 m / z , and CI background mass 55 m / z . The CI reagent pressure was adjusted by using the CI gas inlet valve to obtain protonated methanol ( m / z 33, relative abundance [RA] 100%) and protonated dimethyl ether ( m / z 47, RA 4%) …”