SELECTED-ION FLOW TUBE STUDIES OF S-2(-MOLECULES() REACTIONS WITH A SERIES OF ORGANIC)

A selected ion flow tube (SIFT) has been used to study the reactions o f S-2(+) with a series of organic molecules (as well as H-2, CO, NH3, NO and NO2). These include the hydrocarbons, C2H4, C2H6, CH2CCH2, CH3C HCH2 and C3H8; alcohols and thiols, CH3OH, C2H5OH, CH3SH and C2H5SH; e thers (CH3)(2)O and (C2H5)(2)O; aldehydes and ketones, CH3CHO, C2H5CHO and (CH3)(2)CO; and carboxylic acids and esters, HCO2H, HCO2CH3, HCO2 C2H5, CH3CO2H, CH3CO2CH3, CH3CO2C2H5, C2H5CO2H, C2H5CO2CH3 and C2H5CO2 C2H5. The rate coefficients are generally close to the collisional val ues, with exceptions among the reactions involving the smaller molecul es. Most prevalent are abstraction reactions leading to formation of t he thiosulfeno radical, HS,, or its protonated form; three-body associ ations; and channels leading to formation of the acetyl and propionyl cations, CH3CO+ and C2H5CO+, respectively. Only in reactions involving the alkenes is cleavage of the S-S bond of S; observed. The isomeric molecules in the data set generally react very differently, as would b e expected from reactivity controlled by the position and complexity o f the functional groups. The data are discussed in terms of reaction m echanisms, thermodynamics, and implications for interstellar chemistry . (C) 1997 Elsevier Science B.V.