A selected ion flow tube study of the reactions of H3O+, NO+ and O2+• with some phenols, phenyl alcohols and cyclic carbonyl compounds in support of SIFT-MS and PTR-MS

Abstract: We have carried out a selected ion flow tube (SIFT) study of the reactions of H3O+, NO+ and O2+• with the following 10 compounds: 2-hydroxyphenol, 2-, 3- and 4-methylphenol (o-, m- and p-cresol, respectively), 4-ethylphenol, 1-phenylmethanol (benzyl alcohol), 1- and 2-phenylethanol, 1,4-benzoquinone and cyclohexanone. The primary purpose of this work was to extend the kinetics database to allow these compounds (M), to be analysed in air by selected ion flow tube mass spectrometry (SIFT-MS). The initial step in all the H3O+ reactions is exothermic proton transfer to produce MH+ ions, which are observed as the only products for seven of the ten reactions, but for the three aromatic alcohols, H2O molecule elimination occurred from the nascent MH+ ions producing the corresponding hydrocarbon ion. This is an essential point to recognise when exploiting proton transfer to analyse these compounds using SIFT-MS and proton transfer reaction mass spectrometry, PTR-MS. NO+ reacts with six of the compounds via non-dissociative charge transfer producing M+ ions and this is a valuable route to their analysis by SIFT-MS. In the case of the NO+/quinone reaction, adduct formation occurs giving NO+M product ions, whilst for the remaining three reactions two or more ion products were formed. All the O2+• reactions proceeded via charge transfer with multiple ion products in most cases. A sample analysis is carried out to indicate the value of simultaneous use of both H3O+ and NO+ precursor ions to analyse a mixture containing some of these compounds. [Copyright &y& Elsevier]