Methyl group transfer upon gas phase decomposition of protonated methyl benzoate and similar compounds

Abstract

Gas phase decompositions of protonated methyl benzoate and its conjugates have been studied by using electrospray ionization-collision induced dissociation-tandem mass spectrometry. Loss of CO molecule, thus transfer of methyl group, has been observed. In order to better understand this process, the theoretical calculations have been performed. For methyl benzoate conjugates, it has been found that position of substituent affects the loss of CO molecule, not the electron donor/withdrawing properties of the substituent. Therefore, electrospray ionization-mass spectrometry in positive ion mode may be useful for differentiation of isomers of methyl benzoate conjugates.

Differentiation of bisphenol F diglycidyl ether isomers and their derivatives by HPLC-MS and GC-MS—comment on the published data

“…It is well known that electron ionization mass spectra of 1,2-disubstituted aromatic compounds are substantially different from those of their positional isomers. There are a number of examples that in ESI conditions the ortho effect also takes place [25][26][27][28][29][30][31].…”

Intramolecular hydrogen exchange prior to methanol loss from protonated methyl benzoates bearing different ring substituents under CID conditions

“…It is worth mentioning that the ions at m/z 124 and 123 (Figures 1 and 2s-4s) observed for meta and para isomers are formed as a result of the loss of CO 2 molecule (process discussed in details previously 16 ).…”

“…It is worth adding that the product ion spectrum of [C 6 H 5 COOCD 3 +H] + has shown that the hydrogen atoms from methyl group are not directly involved in the hydrogen exchange. 16 It is also worth adding that the loss of water molecule from protonated benzoic acid is also accompanied by intramolecular hydrogen exchange as shown by the product ion spectra of respective deuterium-containing ions. 17 In this work, we decided to study the influence of substituents on the hydrogen exchange for methyl benzoates bearing different ring substituents.…”

“…The product ion spectra were taken on a Waters/Micromass (Manchester, UK) Q-TOF Premier mass spectrometer (software MassLynx V4.1, Manchester, UK) as described previously. 16 Of course, the full scan mass spectra were also obtained; exemplary full-scan mass spectra are shown in supporting information (Figure 11s Methyl (D 3 ) anisates (supporting information Figure 10s) have been synthesized as follows: To stirred solution of 200 mg of corresponding methoxybenzoic acid dissolved in 3 mL of CD 3 OD, 0.5 mL of SOCl 2 has been added dropwise. The resulting mixture was refluxed over 2 hours.…”

“…Namely, the product ion spectra of [C 6 H 5 COOCH 3 +D] + and [C 6 D 5 COOCH 3 +H] + have shown that part of the eliminated methanol molecules contain hydrogen atoms originating from the aromatic ring. 16 In other words, the loss of methanol from protonated methyl benzoate is accompanied by intramolecular (intraionic) hydrogen exchange (for the ions [C 6 H 5 COOCH 3 +D] + and [C 6 D 5 COOCH 3 +H] + , we deal with intramolecular H/D exchange). It is worth adding that the product ion spectrum of [C 6 H 5 COOCD 3 +H] + has shown that the hydrogen atoms from methyl group are not directly involved in the hydrogen exchange.…”