A selected ion flow tube, SIFT, study of the reactions of H 3O +, NO + and O 2+ ions with a series of diols

Abstract

A selected ion flow tube study has been carried out of the reactions of H 3O +, 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, HOCH 2CH 2SH). The reactions of these species with H 3O + ions are assumed to proceed via exothermic proton transfer, their rate coefficients, k, 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 H 3O + reactions the protonated parent ions, MH +, are always minor product ions. (MHH 2O) +, resulting from the loss of H 2O 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 H 2O 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.