A selected ion flow tube, SIFT, study of the reactions of H3O+, NO+ and O2+ ions with a series of diols

A selected ion flow tube study has been carried out of the reactions of H3O+, NO+ and O-2(+) with 1,2-ethanediol (ethylene glycol), 1,2- and 1,3-propanediol, 1,2-, 1,3- and 1,4-butanediol, 1,5-pentanediol, 1,2-cyclopentanediol and 2-thioethanol (or 2-mercapto-ethanol, HOCH2CH2SH). The reactions of these species with H3O+ ions are assumed to proceed via exothermic proton transfer, their rate coefficients, k(c) being equal to the calculated collisional rate coefficients, k(c). On this basis, the experimental k values for most of the NO+ and O-2(+) reactions are also close to their respective k(c) values, although the k values for three of the NO+ reactions are measurably smaller than their k(c) values. In the H3O+ reactions the protonated parent ions , MH+, are always minor product ions. (MH-H2O)(+), resulting from the loss of H2O from the nascent MH+ ions being the major product ions. Three-body rate coefficients are derived for the association reactions of these product ions with water molecules. The most common process that occurs in the NO+ reactions is hydride ion transfer producing (M-H)(+) ions, but for the 1,4-butanediol and 1,5-pentanediol reactions, hydride ion transfer and parallel H2O elimination occur. The O-2(+) reactions all lead to multiple product ions, which must result from very diverse fragmentation processes. The value to selected ion flow tube mass spectrometry of these kinetic data is briefly alluded to. (Int J Mass Spectrom 218 (2002) 227-236) (C) 2002 Elsevier Science B.V. All rights reserved.